Wait what
If we brought a laptop to school in England it would be confiscated till the end of the week most likely
At most schools, yes.
If you're in College or Sixth Form you'd generally be allowed to take it in.
It is a very handy and sometimes important tool for college work.
So long as you use it when it's appropriate, most UK Colleges don't mind you using them.
But in order to prevent it being stolen...
Make sure you have it properly locked down.
If possible, engrave your name upon the casing or such, as well as any other personal information that would help it get back to you.
You can get GPS tracking to ensure that if it does get stolen or goes missing, you know where it is.
Ensure you have it in a carry-case that you can look after. (Why wouldn't you? You'd hardly want to carry a laptop and a power-cable/pack around all day in your hands)
And really, just keep it with you.
Don't leave it in rooms if you have a break between lessons.
Don't leave it in places where it is likely to be taken.
Don't leave it with anyone you don't know or trust.
Get a locker at school. Leave it in your locker when you have lessons that you can't take the laptop to. (PE for example).
And if you do leave it in a room, make sure there is someone trustworthy in there, like a friend or a teacher.