To be honest, I've been thinking about quiting my 6th Form too. Luckily I don't have it as bad as you, and only have to do 3 A Levels in the 2nd year.
If you really aren't happy, then try and see if you can start a course at college or something. If not, it's best to talk to your teacher, to try and get some help with things. Or just stick it out.
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