don't just crack CLAT, come hack CLAT with us.
I do recall my one of my friend's friend (who I later befriended but I've never asked her this) having taken CLAT in 11th grade. She got NUJS that year and went on to get NLSIU. I began my prep in twelfth grade, so I was never in this position myself.
I can't think of any problems as such, except they might catch you next year when you seek admission to college. If you are willing to take the risk and assuming it's allowed and legit - it's a very big advantage to soak in the pressure and experience the atmosphere first hand.
But you could always attempt some other exam like SET for that feel so it's your call.