What does it mean when your teacher hits on you?

Well, it seems you started to get worried right when your friend said, the teacher was hitting on you. My guess is that maybe your friend was just joking around. I say you should just ignore it, and if it seems like he really is physically interested in you, to the point it gets out of control report him.

It means you report him to the principal he should not misuse your trust that way. If he was not a teacher i would say go for it but no teacher should hit on a student

Well, I can tell you by experience that if he stares at you through out the whole class, he feels attracted by you. However, if he stares like once, no. Then, I can also tell you by experience that older guys start looking at you with different eyes once you mature. You can tell this by his change in behaviour. For example, thought the first semester of school I was an immature brat who kept bugging my teacher in order to get his attention. Whereas, during the second semester I stopped bothering him, payed attention on class and put effort into my assignments. As a result, he realized that I wasn't this little girl, but someone more mature. Followed by that, he started showing he was interested in me by flirting. So, based on this, I can tell you that you teacher definitely noticed that you have changed in a positive way by maturing and that now he is probably interested in you. Now, it is up to you to get him even more interested by flirting. Good Luck!

Don't be alone with him and don't excessively flirt back.

Honestly, that happened a lot in high school and as long as you don't be a total slut and sleep with him - no problem. He's probably one of those losers that only became a teacher so he could consistently have access with underage girls.

On the plus side, you will never have to worry about getting in trouble or failing the class!

Never be alone with him!

And it means he's a creep - if he really is hitting on you.

Don't do anything! It's wrong for him to flirt if he is even realizing he is flirting. I know it's flattering and even more so when the teacher is cute (there were a couple of them in my schools ;)) And it's fine to have crushes as long as it stays innocent.
He could lose his job and possibly never be able to teach again and you would lose respect of many if anything happens between the two of you. NOT a good idea. If your close to being out of school, then pursue all you like AFTER you graduate.