He is too young to not to go to school

Basically, the grammar is not right.

Well, the sentence could be modified in this way if you still want to use the same wordings.

He is too young for him not to go to school or He is too young for not going to school.

他太年輕,不能不讀書
He is so young that he cannot be not getting an education at school.

問題原意是:他太年輕,不能不讀書
He is too young to not to go to school.
He is too young to not going to school
(Both sentences are wrong in grammar, no such phrase written as:
"to not to go to / to not going to" )
I would put it as:
He is too young to abandon schooling.
abandon - (verb) 放棄,中止
schooling - (noun)學校教育;培養

問題原意是:他太年輕,不能不讀書
He is too young to not to go to school (In English to not to go to 是不對和沒這句語的). 應寫為:
He is too young to quit school.
quit = 放棄, 退出, 離開, 或停止.

It's not correct.
The sentcence should be:
1. He is not old enough to go to school.
2. He is too young to go to school.