Realistic exercise per day/ week

I was wondering about the recommended amount of exercise. I think I'm spending enough time on it in addition to school, but wouldn't like to fall behind. Most important to me is finding exercise that actually fits into my time. I currently swim, work at the RSPCA, weight train, do stretching exercises/ pilates whenever possible and walk every day at least, but I'd really like a basis for routine. I'm 16, 58kgs and 163cms. What works for you?

Yikes...just keep what you're doing. You're only 16.

Thanks. :)