You don't know if he's single.
The majority of people are not, after their 20s.
He went through a female dominated course. He works in a female dominated profession. Even outside the school, any courses/training etc he does will be female dominated.
He's attractive, has a good job, and a job that is particularly attractive to women in a man (good with kids).
The chances of him being single are low.
That's if he's even definitely heterosexual, which you don't know for certain.
(And I wouldn't ask directly about a missus/gf - in case it could be represented as fishing about his sexuality).
You also don't know if he'd want to dare someone with two kids when he had no kids of his own. Lots of people (even more so men ime) don't want to.
(He, more than most people, wool be aware of the challenges and issues and complications children present as they go through childhood etc.)
You also don't know if he'd specifically want to date your child's mother. He knows your son quite well already (compared to a relative stranger thinking of dating you) and is aware of any issues, and might - without disliking him in any way, - not want to become an eventual stepfather to him.
At the very least he may not want to contribute to instability in his life if it weren't to work out. He may feel more responsible on that front than a stranger.
All this is totally irrelevant until you establish if he's single.
Even if he is, he may not want to muddy the waters at school by dating a pupils parent, even after he's taught them.
Or he may not see a single Mum as serious relationship material and may only consider a fling, or not want to get involved because he knows it would only be a fling.
You really sound like you need to set up a sitter and get out more dating and socially wise.