Personally I think that we could do better by tailoring every student’s education to their abilities. Put in simplest possible terms, we could arrange classes by complexity rather than by year. Have one class for addition and subtraction, another for multiplication and division, then geometry, algebra, etc, etc. Then let students graduate from one to the next based on proven ability rather than by age. Do the same for language, history, etc. Let every student proceed through the courses at their own speed.