we are in Illinois and kids must be 14 by Sept 1 for 9th grade. However, holding your kids back seems to be a BIG preference here....my son knows some kids who have May bdays and were "red-shirted" ( parents choice to hold back), so they were 15 in May, and will be 16 just before school ends in June. It is a big gap for my kid who turned 14 end of August and went. There can and usually is a wide range of ages in each grade level. Some hold back for maturity , some so their kids can br physically larger for sports etc., some are for what may apply to you, their home has different ages...one boy is from Croatia and they start ( or at least he did) kindergarted a year later, 6-7, so he is older, but started when he was supposed to back there and then when they moved here, he went to his correct grade for him, not according to Illinois age.