So I had this issue a few times before in another save (both kids regular primary school there) that my kids wouldnt go to school, usually fixing the homeworld fixes it but ... nope. Not this time.
I reset everything, reset the lots, tried to fix the homeworld and yet when school-bus time hits it jumps back to "1 day and 2 hours" Forcing them to school via NRaas works but only for that one day. In this save 3 kids are at boarding school, 1 home schooled, 1 in regular school & 1 in music school. I plan to move the home and music school kids to regular school in a sim week for story telling purposes. The music and primary school kid dont leave at 7am like I said, the home schooled kid still is required to do daily homework projects after 10am so it has not been affecting her.

they all went to school fine until a week before the eldest birthday which his birthday is when I plan moving him to the regular highschool

Is anyone in town (besides the teachers) going to school? Might it be summer vacation?

the issue started in spring, it just hit summer now so I do not think vacation is the issue.

I am not sure if anyone is going to the schools. I will try to keep an eye on the buildings around 9am.