HERRMANN, Chief Justice:

In this appeal, we must decide whether the Superior Court committed reversible error when: (1) it failed to instruct the jury expressly to disregard a certain statement made during closing argument by counsel for the defendants; and (2) it refused to instruct the jury that actions of certain of the defendants could constitute negligence per se.

I.

At trial, counsel for the defendants stated in his closing argument:

"Mr. Schmittinger implied that there were not four teachers on the playground. If there were not four teachers on that playground, then, in the course of my case, I have perpetrated a fraud on you, because I have called as witnesses these two teachers here, Mr. Stevenson and Mrs. Scrimshaw, and Mrs. Waters and Mrs. Tyndall. If they were not on that playground that day, then I, as a lawyer, have put witnesses on this witness stand as part of a fraud. If you believe that that is the case, then, by all means, return a verdict for the plaintiff.

"But that was not the case. I think you are convinced of that, that is, that there were these four teachers. These four teachers have testified that they were there, and I assume that you believe them. I do, and I just assume that you do."

After objection by the plaintiffs' counsel, the Trial Court instructed the jury as follows:

"All right, ladies and gentlemen of the jury, there is a fine distinction that is difficult for judges and lawyers, who are used to this sort of thing, to determine when counsel and lawyers are interjecting their own personal beliefs about what has been done in a trial, as opposed to telling you that certain things have been proved by the evidence in this case. Lawyers generally may not put their own reputation or their own beliefs or their own veracity or anything else, in as part of their argument.

"For instance, the difference is maybe best illustrated by may saying that we are talking about a case involving a car stopping for a red light and the lawyer says, `Members of the jury, we have definitely proven to you that my client did not go through that red light,' as opposed to saying, `Members of the jury, I go to church every Sunday and I am an ordained minister, and I tell you that I know that he did not go through the red light.'

"Do you see the difference?

"All right, that is enough said. A lawyer may not do that, and Mr. Elliott is going to stop it, if he did cross that line. He may not interject his own personal belief as to whether a witness said something that was true or not true."

The plaintiffs' counsel, nevertheless, renewed the objection, claiming that the jury should have been expressly instructed to disregard the objectionable statements. The Trial Court, however, took no further action.

Later, in the course of the trial, the Trial Court refused the plaintiffs' request that the jury be instructed that noncompliance with certain provisions of the Teacher's Handbook, promulgated by the School District Board of Education regarding the supervisory responsibility of teachers, amounted to negligence per se. The jury subsequently returned a verdict in favor of the defendants. After the close of trial, the plaintiffs filed a motion for a new trial, which was denied by the Trial Court. Plaintiffs appeal; we affirm.

II.

The plaintiffs' first contention on the appeal is that the Trial Judge's failure to explicitly instruct the jury to disregard the improper remarks of counsel for the defendants constituted reversible error and requires a new trial. It is contended that the credibility of the school teachers, who testified that they were on the playground at the time of the injury, was a crucial issue in the trial; that the failure of the Trial Judge to specifically admonish the jury to disregard defense counsel's remarks regarding the credibility of these witnesses did not erase the serious prejudice caused by the remarks.

While we agree, of course, that it is improper for counsel to comment on the credibility of witnesses from personal knowledge or from evidence not on the record, every such comment is not necessarily reversible error. The question is whether the improper comments caused sufficient prejudice to the complaining party to warrant reversal or whether the prejudice was cured by the cautionary instructions given by the Trial Court. See University of Delaware v. Munson, Del.Supr., 316 A.2d 206 (1974). As we stated in Chavin v. Cope, Del.Supr., 243 A.2d 694, 696 (1968): "Ordinarily, an appropriate instruction to disregard the statement is sufficient to avoid prejudice to the defendant, but an incident may be so flagrant as to require a mistrial. The question is always one for the sound discretion of the trial judge."

We can find no abuse of discretion by the Trial Judge in this case. The instruction clearly conveyed to the jury that counsel for the defendants had, inadvertently it seems to us, overstepped the bounds of propriety. The omission of explicit language directing the jury to disregard counsel's statement was not reversible error; the clear import of the cautionary instructions given was adequate as an admonition that the jury was to ignore the improper comments.

III.

The plaintiffs also contend that the Trial Court erred in refusing to instruct the jury that if the defendants acted in violation of the above quoted provisions of the Teacher's Handbook, they would be guilty of negligence per se. The plaintiffs rely heavily on Sammons v. Ridgeway, Del.Supr., 293 A.2d 547 (1972), in which this Court held that violation of rules and regulations, promulgated by the State Board of Education governing the design and operation of school busses, constituted negligence per se. This Court there stated:

"It is clear that (1) Regulations 9 and 10 were promulgated for the safety of school children; and (2) they have the force and effect of statute. It follows, under our law, that the Trial Court correctly applied to those Regulations the negligence per se rule."

We are unable to accept the plaintiffs' argument. Several controlling differences exist between the regulations here claimed to have the force of statute and those involved in Sammons: (1) In Sammons, the regulations were promulgated pursuant to 14 Del. C. § 2901, which specifically required the State Board of Education to adopt rules and regulations governing school bus "design and operation", and mandated that their application be statewide; in the instant case, on the other hand, the Statute [§ 1049(1)] only requires rules and regulations "for the conduct and management of the schools", with no further specificity; (2) Rule No. 10, supra, which forms the basis of this action, also lacks the specificity required for the invocation of negligence per se; it only requires vaguely that a playground area be made "pleasant and safe" and that "[s]taff members on playground duty * * * be aware of what is happening on the playground at all times"; it contains no sufficiently specific statement of supervisory duty, the violation of which would constitute negligence as a matter of law; and (3) those who violated the Sammons bus regulations were subject to the statutorily defined civil penalties of breach of contract and removal. 14 Del. C. § 2902 and § 2903. Section 1049 here involved, on the other hand, merely grants general rule-making powers to each school district to aid them in their statutory duty to administer and supervise the schools in the district, 14 Del. C. § 1043, with no penalty or enforcement provision behind § 1049 or Rule 10, such as those which augment § 2901 in Sammons. It would seem highly illogical to permit a rule or regulation to be the foundation of a negligence per se charge when there is no punishment, civil or criminal, for its violation. See 57 Am.Jur.2d Negligence § 238 (1971).

We conclude that the rules and regulations here in question do not carry the force and effect of law and that, therefore, there was no reversible error in the Trial Judge's refusal to charge the jury on the issue of negligence per se.

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Affirmed.