When is the right age to start lifting weights and are there any particular exercises that shouldn't be done until highschool?

DD,
Your question is a bit broad. On answer could be...What are you looking for?

Are you looking to gain size and power?
Are you looking to tone or cut up?
Are you looking for exercises specifically for BB?

As far as age goes, I started at 13. But I played football where lifting for size, power and explosion where necessary. If you're in baseball I would think you could do some standard exercises for chest, arms, back and legs. But I would stick to more higher repitions. Although before stepping into any weight room, you should consult with your physician, strength coach or head coach.

I would suggest that you post you question in the Strength and Conditioning Forum for more results