If the sex education lessons children get from primary school onwards included how to say NO and mean it some of the problems would disappear.
I don't think the pregnancies of the very young girls, say under 14s are due to drugs or alcohol, if they are why have the parents allowed this , are they just turning a blind eye when she comes in worse under the influence.
In schools the morning after pill is handed out more or less on demand, why don't these school nurse ask the girls to let them test them to see if they have caught anything and explain on a one to one basis the consequences of these diseases. No test or talk if they refuse just hand out the pill, but if they can only get one or two girls to test positive I am sure these girls would get others that they know or believe to have been with the same lads to get tested.