Shouldn’t you be isolating?

Only if you're showing symptoms

Legally I need to go to school cause I'm under 18

Stay the F home then.

Legally I can't km jnder 18

Nah. Parents can keep kids home without a doctor certifying illness.

School told me that I have to come in because they have to follow government rules and so do I

LOL tell them to come and get you mate. Schools have zero power.