A little hippie promblem!!!!!

eno is being trollish, so in general, it is best to disregard advice that is rather silly.

Ask your parents WHY they want your hair cut: it could be the bangs in eyes is driving them batty more so than an overall length.
they could be thinking "if he looks 'normal' he'll BE normal."
That's where all the culturally-loaded perceptions of hair length , esp. on males comes in.
Can you find a middle ground?
Maybe if you pull all As or hit an honor roll, or whatever, you can do what you want with your hair?
that'd be win-win, mostly.