I read a lot of these very quickly. I commend all of you for being engaged in your children's lives to hopefully make the correct decisions.
My oldest, a late spring birthday, was clearly one of the youngest in his class and he matured later. He had braces on as a junior in HS. Academically, he was where he needed to be, but he was "young." We chose academics over athletic prospects and it worked out. He played college sports at a very high-end academic school.....all American there. If we held him back, he probably would have been at a Stanford or Harvard with an additional be year, but it all worked out.
No clear playbook. A lot of plusses and minuses. I am glad to see the engagement of parents here versus school boards or k-third grade teachers telling u what is best for your children. Get their feedback, but u decide.