The best and only starting point for a healthy and productive workout is a tailored nutrition plan that reinforces stamina, your attention span, and your energy level, no matter what physical work you undertake.
Breakfast is the most important of all your meals. A carbohydrate breakfast that includes grains, fruit and dairy. You should target a breakfast that starts the metabolism, then multiply small meals throughout the day, with variety, as appose to the usual lunch and dinner only.
Your reaction to certain foods should be noted and recorded. In fact, every pitcher that I've coached over my 28 years has maintained a log of what was consumed during the day. Why? Because certain foods your body will crave as energy makers - and NO, don't include Snicker bars and the like.
Once you have a daily meal plan, get yourself aware of the bathroom breaks that'll come with such a nutrition plan. Why? If your breakfast starts and finishes around 6:30am to 7:00am, more than likely you're going to need a bathroom break around 9:00am... so, if you're in the middle of a class at or about that time (9:00am) the last thing that you'll want to do is to break class for a bathroom break.
Exercise is an important part of your pitching experience, so without knowing your physical attributes and your age, body type - slim, stocky, etc., you're going to need a pitching coach to help you. He/she, will take you needs and tailor a diet and workout plan to suit your particular physical condition - stamina, past health history, family and social commitments, and a host of other particulars.
I know my response is rather lengthy, but, workouts in and of themselves are NOT a stand-a-alone activity when it comes to developing pitchers. (** not that I'm assuming that your going to do workouts only) Starting out right at a young age to pursue a PROGRAM is the way to go.
I hope this gives you a direction and helps you enjoy your baseball experience.