Can teachers tell if the student...?

That all depends upon the situation. Some students have a crush but show no evidence of it.

If a teacher is tuned in to each of his/her students behaviors, he/she should be aware. Students have developed crushes on teachers since the dawn of the student/teacher relationship. But ultimately it shouldn't matter if teacher recognizes it or not. Don't act on it, it is unhealthy. If you truly like your teacher, just sit back and enjoy the view in class. 10 to 20 years from now you'll rememeber this time fondly.

what??

A good teacher should be able to read the eyes and body language of a student. (its not infallable but it does give you a lot of information to work with) I teach adults and I have to deal with that all the time. (its both flattering and frustrating at the same time, but mostly its an unwanted distraction)

Probably, they can sense it..Remember, adults were kids at some time. so they might know some of the behavior children show when they like someone one. Possibilities are more towards, yes they can!

no, im a teacher, and we are too busy thinking about our job and our own love lives to worry about the students. not to be mean but we don't try to think about the students in a friendly or romantic way. even being just friends with a student is not very professional. we keep our distance!

certainly yes if student makes it obvious. but we got better and more important things to worry about than students' feelings; LIKE THEIR EDUCATION. but I ignore when i sense that. and if i sense kid is really messed up, i just run it by my supervisor, just in case situation gets any worse

Usually, but not always. I was able to tell right away when one of my husband's students had a crush on him. Kids are generally transparent when it comes to stuff like that.