I am (as penance for my sins in a previous life) a school governor.
It is very important that you get a copy of your school's complaints policy - it may even be on their website - and then follow it. If you do need to take this beyond the level of the school/governing body, they will be looking first to see that you went through the school's complaints process (and with what result).
Where you go after the school/GB is, of course, up to you, but I don't see what you could gain by writing to (say) your MP. Your MP may be able to bring pressure to bear - if s/he chooses to take up your case - and you may gain some publicity that way, but the MP has no formal responsbility for your school or any other. LEA seems more likely if you need to escalate the complaint.