I'm an 18 year old girl and I left school a few months ago and after I left, my former art teacher (who taught me from year 8 - year 11) got in contact with me on Facebook. We met up for a night out last week and he told me he finds me unbelievably attractive and we kissed. We met up again today and he told me that we could never be together because I'm an ex-student of his. Is it illegal? What would happen if the school found out. I really like this guy and he's not a weird perverted guy, he's only 27.

It's not illegal, but he could lose his job if the school finds out. This is not behavior a school would find appropriate.

RED FLAG_

He tells you that you can never be together, yet he meets up, after contacting you on Facebook.

Wonder what his intentions are? Secret lovers? Friends With Benefits? You had better be careful, because not only is this inappropriate, but highly suspicious. I mean HIGHLY suspicious!

My thinking is that he told a friend about contacting and meeting you. And the friend asked him if he was crazy and wanted to lose his job. So he told you you can't be together.

I find his behavior very inappropriate.
You need to stay away from him. The fact that he waited until you were 18 and then contacted you tells me he's trying to keep himself out of trouble, but contacting you was just IMO wrong on a lot of levels.
He maybe only 27 but what he is doing is creepy.
Makes me wonder how many other graduates he's contacted.