NATHANIEL R. JONES, Circuit Judge.

Andrew Meilton, a junior high school teacher in the Columbus City School System, was reprimanded by his supervising principal for engaging in "unprofessional conduct" while acting in his capacity as building representative of the Columbus Education Association. Meilton filed suit in the federal district court alleging that the letter of reprimand placed in his personnel file by his principal was predicated on Meilton's zealous advocacy as a union representative of a fellow teacher's complaint. The district court, after a nonjury trial, entered judgment for defendants, holding that the principal's letter of reprimand was not motivated by a desire to curtail or penalize Meilton's expression of free speech. Because we hold that the district court improperly applied to this case the Supreme Court's decision in Bishop v. Wood, 426 U.S. 341, 96 S.Ct. 2074, 48 L.Ed.2d 684 (1976), and erred in its failure to apply the test in Mt. Healthy City School District Board of Education v. Doyle, 429 U.S. 274, 97 S.Ct. 568, 50 L.Ed.2d 471 (1977), we reverse.

I.

Plaintiffs are the Columbus Education Association ("CEA"), the recognized collective bargaining representative for teachers in Columbus, Ohio, and Meilton, the CEA building representative at Barrett Junior High School. The named defendants are the Columbus City School District, its Superintendent, each of the members of the Columbus Board of Education, and Charles Pollock, Principal of the Barrett School.

On Friday, February 15, 1974, Judy Davis, the school librarian, disciplined two students for making excessive noise in the school's main office. Davis attempted to quiet the students, touching one of them in the process. Donald Newman, the Vice Principal, observed this interaction and asked Davis to step into his office. Newman criticized Davis' disciplining of the two students. Later that day Davis related these events to Meilton. Meilton, in his capacity as the CEA building representative, requested a meeting with Charles Pollock and Judy Davis to discuss the matter. A meeting was scheduled for the next Monday.

At the Monday morning meeting Meilton, speaking on Davis' behalf and with her consent, explained why Davis was upset and presented her complaints. Before the meeting was formally adjourned, Meilton indicated that he had a class waiting and rose to leave. Davis also left the meeting at that time.

Shortly after the meeting, Pollock circulated a memorandum which announced that an additional meeting would be held that afternoon. At that meeting Pollock indicated his intention to discuss Meilton's conduct. Meilton requested a postponement of the meeting until he could secure CEA representation and left the meeting. Davis stayed. In his deposition, Pollock indicated that he only wished to discuss the "matter" informally. On February 27, 1974, Pollock sent a letter to Meilton stating that Meilton's conduct had been unprofessional and unacceptable. A copy of the letter was placed in Meilton's personnel file. Plaintiffs seek to have the letter removed from the file.

II.

The district court held that the defendants had not infringed on plaintiffs' First Amendment rights. It relied heavily on Bishop v. Wood, 426 U.S. 341, 96 S.Ct. 2074, 48 L.Ed.2d 684 (1976), where the Supreme Court in dicta described the rights of public employees in the following manner:

The federal court is not the appropriate forum in which to review the multitude of personnel decisions that are made daily by public agencies. We must accept the harsh fact that numerous individual mistakes are inevitable in the day-to-day administration of our affairs. The United States Constitution cannot feasibly be construed to require federal judicial review for every such error. In the absence of any claim that the public employer was motivated by a desire to curtail or to penalize the exercise of an employee's constitutionally protected rights, we must presume that official action was regular and, if erroneous, can best be corrected in other ways. The Due Process Clause of the Fourteenth Amendment is not a guarantee against incorrect or ill-advised personnel decisions.

Id. at 349-50, 96 S.Ct. at 2080 (Footnote omitted.).

The district court found that the letter of reprimand was not motivated by a desire to curtail or penalize plaintiffs' free expression of speech, stating:

I read this letter to be merely an expression of Pollock's opinion that the manner in which Meilton chose to exercise his freedom of speech was inappropriate and unprofessional under the circumstances, and beyond the scope of his activities under the collective bargaining agreement. Absent a finding of an intent to deprive, or an actual deprivation of, some constitutional right, the expression by a school administrator of his opinion as to the conduct of a teacher employed in that school is a matter within the internal personnel policies of the school, or at most a matter cognizable under state law.

The district court's finding that the principal did not intend to violate plaintiffs' constitutional right of free expression is predicated upon its application of the above-quoted dicta from Bishop. Bishop is inapposite to the issue presented for review. The Supreme Court in Bishop analyzed the constitutionality of the dismissal of a municipal employee. Bishop argued that in dismissing him the City of Marion, North Carolina failed to comply with the Fourteenth Amendment's due process requirements of notice and opportunity for hearing as set forth in Perry v. Sinderman, 408 U.S. 593, 92 S.Ct. 2694, 33 L.Ed.2d 570 (1972), and Board of Regents v. Roth, 408 U.S. 564, 92 S.Ct. 2701, 33 L.Ed.2d 548 (1972). Unlike Bishop, plaintiffs in this case do not argue that the defendants' actions deprived Meilton of a property interest, although they do allege harm to reputation. Plaintiffs' main claim is that the letter of reprimand has a chilling effect on their exercise of free speech and association. Agreeing with plaintiffs' characterization of the harm, we conclude Bishop is inapposite to the issue to be decided. Consequently, we do not defer to findings of the district court which are guided by the application of an improper test.

III.

At issue is whether Pollock's letter of reprimand was written in retaliation for Meilton's zealous advocacy as a designated union spokesperson of a fellow teacher's complaint. Smith v. Arkansas State Highway Employees, Local 1315, 441 U.S. 463, 99 S.Ct. 1826, 60 L.Ed.2d 360 (1979). The Supreme Court in Mt. Healthy and in Pickering v. Board of Education, 391 U.S. 563, 88 S.Ct. 1731, 20 L.Ed.2d 811 (1968), established the principles which guide our resolution of this appeal. The Supreme Court in Mt. Healthy fashioned a "test of causation which distinguishes between a result caused by a constitutional violation and one not so caused." 429 U.S. at 286, 97 S.Ct. at 575. The court reasoned that "[t]he constitutional principle at stake is sufficiently vindicated if such an employee is placed in no worse a position than if he had not engaged in the conduct." Id. at 285-286, 97 S.Ct. at 576. Mt. Healthy sanctioned the application of the following procedure to determine causation:

Initially, in this case, the burden was properly placed upon respondent to show that his conduct was constitutionally protected, and that this conduct was a "substantial factor" — or, to put it in other words, that it was a "motivating factor" in the Board's decision not to rehire him. Respondent having carried that burden, however, the District Court should have gone on to determine whether the Board had shown by a preponderance of the evidence that it would have reached the same decision as to respondent's reemployment even in the absence of the protected conduct.

429 U.S. at 287, 97 S.Ct. at 576 (Footnote omitted).

Applying these principles, we hold that Meilton's zealous advocacy as a union spokesperson of a fellow teacher's complaint was a substantial factor in the principles letter of reprimand.

It cannot be gainsaid that the First Amendment protects the rights of individuals to speak freely, to advocate ideas, to associate with others, and the rights of an association to engage in advocacy on behalf of its members. Smith, 99 S.Ct. at 1827; NAACP v. Button, 371 U.S. 415, 83 S.Ct. 328, 9 L.Ed.2d 405 (1963). Thus, a reprimand to retaliate against the zealous representation by a union spokesperson of a member's grievance impermissibly infringes upon the constitutional right of free association, recognized in NAACP v. Alabama ex rel. Patterson, 357 U.S. 449, 78 S.Ct. 1163, 2 L.Ed.2d 1488 (1958), and Shelton v. Tucker, 364 U.S. 479, 81 S.Ct. 247, 5 L.Ed.2d 231 (1960), and the right to free speech recognized in Pickering.

It is undisputed that the principal's letter reprimanding Meilton for "unprofessional and unacceptable conduct" was written in response to Meilton's representation of a fellow employee. One cannot separate Meilton's zealous advocacy from his role as a union representative. Thus, we find that plaintiff established a prima facie case that the reprimand was predicated on constitutionally protected activity. The burden then shifted to defendants to prove that its interest in the efficient administration of education outweighs the plaintiffs' free speech and association rights. Pickering v. Board of Education, 391 U.S. at 568, 88 S.Ct. at 1734.

Defendants argue on appeal that the First Amendment does not protect statements made in private on a matter not of general public concern. The Supreme Court held in Givhan v. Western Line Consolidated School District, 439 U.S. 410, 99 S.Ct. 693, 58 L.Ed.2d 619 (1979), that the First Amendment does protect an employee's private communications with an employer. In Givhan, the employee protested racially discriminatory employment policies. The Court stated that the Pickering balancing test may involve different considerations for private statements:

When a teacher speaks publicly, it is generally the content of his statements that must be assessed to determine whether they "in any way either impeded the teacher's proper performance of his daily duties in the classroom or . . . interfered with the regular operation of the schools generally." (citation omitted). Private expression, however, may in some situations bring additional factors to the Pickering calculus. When a government employee personally confronts his immediate superior, the employing agency's institutional efficiency may be threatened not only by the content of the employee's message but also by the manner, time, and place in which it is delivered.

Id. at 415, n. 4, 99 S.Ct. at 696.

Relevant factors justifying a state's regulation of its employees' speech include the content of the speech, coworker harmony, maintaining discipline by immediate supervisors, need for personal loyalty and confidence between workers and supervisors, Pickering v. Board of Education, 391 U.S. at 569-70, 88 S.Ct. at 1735-1736; and the time, place and manner in which the speech is delivered, Givhan v. Western Line Consolidated School District, 439 U.S. at 415, n. 4, 99 S.Ct. at 696. Defendants offered no evidence justifying its regulation of its employees' exercise of free speech. Based upon our review of the record and oral arguments on appeal, we conclude defendants have failed to offer any rationale to legitimize the reprimand.

Plaintiff was not disruptive of school operations. Tinker v. Des Moines Ind. School District, 393 U.S. 503, 89 S.Ct. 733, 21 L.Ed.2d 731 (1969). There is no factfinding of disruptive effect. The conversations were in private and involved the disciplining of students by one of the teachers whom Meilton represented as a zealous advocate. We fail to see any significant or material disruptive effect. See Barnasconi v. Tempe Elementary School District No. 3, 548 F.2d 857 (9th Cir. 1977).

Nor did Meilton engage in any egregious misconduct that would take his speech outside the limits of protected activity. Meilton's conduct did not involve direct public criticism of his supervisor or did not arouse intense animosity among his coworkers. E. g., Sprague v. Fitzpatrick, 546 F.2d 560 (3rd Cir. 1976); Hochstadt v. Worcester Foundation for Experimental Biology, 545 F.2d 222 (1st Cir. 1976).

Meilton's representation of a fellow teacher's complaint followed established procedures and occurred at the time, place and in the manner agreed to by the parties. Givhan v. Western Line Consolidated School District, 439 U.S. at 415, n. 4, 99 S.Ct. at 696. Had Meilton either unilaterally decided to represent a fellow teacher or caused harm to the operation of the school, the State's reprimand would have more legitimacy and the plaintiff's claim to constitutionally protected speech and association would be less compelling.

A union representative must be allowed to be a zealous advocate. The defendant has failed to demonstrate any substantive interest in the forms of evils flowing from plaintiff's activities which can justify the reprimand it has imposed. Brotherhood of Railroad Trainmen v. Virginia ex rel. Virginia State Bar, 377 U.S. 1, 84 S.Ct. 1113, 12 L.Ed.2d 89 (1964). As stated by this Circuit, "[t]o allow any rancorous feelings engendered in this manner to justify a [reprimand] would decimate constitutional protections." Hickman v. Valley Local School District, 619 F.2d 606 at 609 (6th Cir., 1980).

Accordingly, the judgment of the district court is reversed and the case is remanded to the district court. Upon remand the district court shall order the defendant to expunge the reprimand from Meilton's personnel files, and shall consider the appropriateness of an award of attorneys fees, and, if appropriate, the amount of such an award.