Try this. I want you to take some very deep breaths, in through your nose and out through your mouth. Take four deep breaths. Sit up straight in your chair, or stand, and push your shoulders back, lift your chin up so you're looking straight ahead. Now, I know there has been a time in your life when you were strong and I want you to remember that time right now. Bring that memory into your mind right now. Make the pictures in your mind bold and bright colours. If the pictures in your mind are small, bring them closer to you and put them right in the middle, nice and big so you can see them clearly. Remembering the great feelings you had when you were strong and fair and had all the resources you need to deal with anything.
OK, from this place I want you to think about these girls and just see them in your mind. Put the picture of them lower down in your mind, dim their colours (maybe black and white) and then observe what they're doing.
Now, from this position, make a decision about what you're going to do. Remember, you have many choices open to you. You could talk to your tutor, you could stay away from them, you could talk to some people at College about them, you could challenge them directly, you could tease them back or you could do nothing and let it wash over you and just laugh inside as they try and affect you.
Remember, you have all the resources you need to deal with this and I know sometimes i doesn;'t feel like that. Remember to breathe deeply, remember you can be strong, you can handle hard things and remember that sound inside of you laughing gently to yourself.