I completely agree, and my son sounds similar to your kids. My training is as a teacher, so I work with him at home, and he is currently studying 3rd/4th grade material at home in math and reading. Meanwhile he is in a 1st grade class, and even that I had to push for because last school year his mid September birthday was going to have him forced to endure a year of TK, learning to count and learning letter sounds for a 4 year old that was already reading and adding and subtracting with ease. The school allowed him to start kindergarten with him turning 5 in September… but yeah, I am very aware he gets his learning at home, from me. School is mostly social for him. Though, I should give credit to his teacher, who allows him to read with a second grade group (1/2 combo class) and allows him to skip easy worksheets and do multiplication instead.
My opinion is that age based grade levels are an archaic system that should be replaced by ability based levels of schooling. If you are curious, I elaborate here:
It’s Time to Ditch the Archaic Idea of Age Based Grade Levels
Why continue to use an education model developed in 1837, at the detriment to our students?
As far as sports go, he is also performing above age, but that seems to be ok for now. He is on a club (travel) hockey team (at age 6) and will be playing in an 8u rec league starting in March. He might be joining an 8u club team soon too, and doing tournaments at both levels. Hockey at least seems to allow more of a challenge if needed as you can play up, not down.
However, as far as school sports go, I know I hurt his chances, because I made choices for him based on academics, and thus, he is doomed to be the youngest every year, instead of being older than many peers if I had followed the rules and forced him through TK.
Sorry for my novella here, but suffice it to say, I feel like so much of my son’s life is governed by his birthdate and it would be so nice if these arbitrary dates didn’t determine so much of their lives.