Assalamu alaykum brother.
I'm sorry to hear about your uncomfortable environment in class.
I would really recommend you to take it easy regarding this thing, if you deal with it easily, it will fade away faster than intended. For the same purpose do consider the following:
1- Are you sure that they are doing this to bother you or is it just something that's occurring to you? Sorry I ask this way, sometimes when we are a bit uncomfortable in a particular environment we tend to become very self conscious. So I would really ask you to look into it again?!
2- Stay focused. Ofcourse you are attending school for a purpose and that should be your real concern, once you're head down, I'm sure the girls will get a indirect answer and move away. Avoid any eye contact. Resolves a lot of issues.
3- Silence is the best answer to a fool, and actions speak louder than words, therefore your silence and zero reaction will soon be nailed into their brains.
4- Just in case if the situation becomes a bit more unbearable or so, be very blunt and announce your concern. It could be as simple as 'I'd appreciate it if you used the other way to get in or out of the class, thank you' once they have the clarity of your thoughts and firmness I'm sure they will back off.
5- Prayers can do wonders brother. Constantly recite Salwat, ask Allah to help you through the situation.
I hope this was useful