315 for 10 deep reps is a good set right now. Makes a huge difference if you're going down all of the way:
I've seen kids do sets of 10-12 with 315, only going down to about a half squat. I've shown them how to do it (all the way down), and they can't even get ONE rep with 275!
Lets face it, if you couldn't lower the bar to your chest in a bench press, then you wouldn't count the lift. Same with squats
I can squat 135 for 50 deep reps AFTER doing the heavy stuff - it's a fucking trip , believe me. 225 for 25 reps is a bastard too.
A great way to get used to high squatting is to have one workout a week for 5 weeks straight where you just do squats: 20 sets of 20 reps - maybe with just the bar. After that, you have the groove so well that you will just feel the muscles working and not be out of breath.