How Should I Tell My Parents, I'm Being Molested At School ? ( Long Story )?

Here in the UK we have what's called a 6th form Lower 6th form ( Junior Year ) and Upper 6th form ( Senior year ) Anyway there's this teacher in the lower sixth form and he only started working at the school about 1 or 2 years ago and at the beginning of the year, he was your typical young (he's 26) "fun" teacher. He's the type of teacher that students feel they can connect with since he's closer to our age than most of the other teachers are. But lately he's been really touchy with me and other girls in the 6th form. The sixth formers at my boarding school don't have to wear uniforms, so some of the girls wear skirts and in cl he'll pretend to drop his pen or pencil under our desk so can look under our skirts and such. One day I having trouble in his cl and he offered to help me after school. Once he finished helping me I was getting ready to leave and then I felt him put his hands on my shoulders and he whispered in my ear about how "tense I felt" and how he could make me "relax". I felt his hand travel down my backside and up my skirt. I had started to cry and asked him to stop and he told me that it was going to be okay. Finally he had stopped and I went crying back to my dorm room and I told my roommate and mate Christelle what he had did to me and she gave me a hug and told me that it would be okay and that it's something he does to all the girls and it just takes getting use to. Anyway she went on to tell me that he had did something similar to her and her mate Lisa last week. Only that time he had started to touch her on her private parts and Chris told me that she had started to cry and he told her that it was going to be okay and that she was the "student and he was the teacher". She told me that she had a few nightmares but she also knows that she's not the only one that it happens to. Other girls have said that he tries to unhook their bra straps, make them sit on his lap, he says how y we are, One of the worst things that have happened would have to be when this girl Cie said that she and him were alone and she was helping him with something and he made a p at her. He had asked her for a hug good-bye and she didn't think it was appropriate to give him one but he told her that she wouldn't get in trouble so she gave him one and he started to kiss her and he made her kiss him back. She finally pushed him off her. Cie said she was shocked and scared. The worst thing about this whole thing is that there is this girl named Anna and she will be coming to the lower 6th form next year and her and the rest of the girls in her year all they talk about is what a charming, sweet, wonderful, "hot" teacher he is and how they want him as a teacher next year. One day Anna even told me that when she was leaving cl she ran into him and they started talking and Anna was telling him how excited she was about going to the 6th form next year and how she hears what a wonderful and fun teacher he is. He replied that hopefully he'll have her in his class next year because she looks like his "type" of student. Myself and the other girls don't want Anna and and the rest of the girls coming to the 6th form next year, to have to go through what were going through now with him. So me and all the girls decided that we wanted to tell our parents what he's been doing to us. But were scared to tell our parents. What if they think it was our fault ? My dad he noticed that something been wrong and he asks me about it but I don't know how to tell him and I feel like it's my fault. I feel like I wouldn't even know how to begin, to tell him that my teacher is touching me and other girls. The main question is how should we tell our parents ? Most of us feel like it's our fault. Like we did something to turn him on. Most of us are 17.