I was your case last year, I took government and politics at an all boys grammar school but there ended up with two other girls there. Most of them probably have had female contact and won't jump at you with 'hits' and in fact, most of them do nothing.
If your really worried about getting hit on then just ignore them/show your not interested. A-levels are about commitment and I can not stress how important this commitment is. Most of them will also be committed to their A-levels unless their dossers. Don't worry! You go there and just study with effort- no one can touch a girl whose got commitment.