(f) The requirement for approval of an exception to exceed the 20 pupils per kindergarten teacher per session limit or the 25 pupils per teacher limit in grades four through six is waived in schools where the schoolwide pupil-teacher ratio is 25 or less in grades four through six: Provided, That a teacher shall not have more than three pupils above the teacher/pupil ratio as set forth in this section. Any kindergarten teacher who has more than 20 pupils per session and any classroom teacher of grades four through six who has more than 25 pupils, shall be paid additional compensation based on the affected classroom teacher's average daily salary divided by 20 for kindergarten teachers, or 25 for teachers of grades four through six, for every day times the number of additional pupils enrolled up to the maximum pupils permitted in the teacher's classroom. All such additional compensation shall be paid from county funds exclusively. Notwithstanding any other provision of this section to the contrary, commencing with the school year beginning on July 1, 1996, a teacher in grades one, two, or three, or classrooms having two or more such grade levels, shall not have any pupils above the teacher/pupil ratio as set forth in this section.