I my education in the UK too.I think you should go back to your old school,I did once.I was quite unsure,but it worked out great.
However,if you think the new school is better(you said it was good),then you should go there,as the purpose of going to school is to learn.
Do what you feel best. I would say "New School." Meeting new people is way more intresting than looking at old faces everyday. No offence, but its just something different. You would have a greater adventure and an expanding friends list for when you are bored. It also may include greater opportunities.