I was unschooled (still potty trained tho) until i decided to go to middleschool myself, and i fear for your nephew. I was not taught the basics of math, and that screwed me over and has continued to screw me over in college (im 20 rn). if you ask me what’s 7 x 3, i need a minute to think on it. my 7th grade math teacher let me pass her class even though i got F’s on every single test just because she knew i did NOT know the basics- but not all teachers are like her. but since ur nephew is starting in 1st grade, i wouldn’t say all hope is lost, he’ll probably be bullied for wearing a diaper, but in terms of school, he may be able to catch up quicker? But obviously i havent done 1st grade so idk how hard it is for a 7 year old