First, you don't need to be chugging down snacks and shakes between classes. Realize that if you have meals spaced 4-6 hours apart you are still going to be perfectly fine. The need to have so many meals a day is truly personal prefrence. The key thing here is total calories over the course of the 24 hour period.
Protein Intake & Meal Frequency:
http://www.biolayne.com/wp-content/uploads/Norton-J-Ag-Food-Ind-Hi-Tech-2008.pdf
http://www.slideshare.net/biolayne/optimal-protein-intake-and-meal-frequency-to-support-maximal-protein-synthesis-and-muscle-mass
For instance you could easily wake up, have a meal at home, eat a lunch at school, grab a quick snack between classes, eat after school, and then have another meal later at night (or two) which is still 4-5 meals and can easily hit your total caloric intake for the day given you are using proper sources to meet that caloric intake.
For example -
1) Before school: 5-6 Whole Eggs, 3-4 slices of toast, Sugar free jelly or peanut butter, fruit on the side
2) Lunch --> Pack chicken/beef/turkey/tuna etc with you... Rice, and veggies (make a stirfry and just microwave at lunch, very easy and portable (or you could sub in potatoes find what settles very easy for you)
3) Between class or during a break ---> peanut butter sandwich, nuts, dried fruit, beef jerkey, hard boiled eggs, or a protein shake
Other things to consider: Bagels (very caloric dense), banana's, honey
4-5) When you are home.
Beef/Chicken/Turkey/Tuna, Greek Yogurt (Protein)
Pasta, Rice, Potatoes, Rice Cakes, Cereal's, Pancake Mix, Quinoa, muffins, english muffins, oatmeal, cream of rice, cream of wheat, rice cakes (Carb sources)
Nut Butters, Oil's, Whole Eggs, Avocados, Full Fat milk/Dairy Products, Nuts (Fat Sources)
All of these Are great choices, but again your young. when you get home if you want to have a candy bar per say you can easily fit in 200-300 calories with a very fast metabolism and in order to keep your caloric intake up. Don't stress over trying to hit X or Y macros. At your given age as long as you making good choices for the majority of the time and trying to focus on meeting protein/fat intake over the period of the day you are going to be good to go. Sometimes prepping things in bulk and ahead of time goes a long way to help keep you on track.
Again you don't have to walk out of class and chug a protein shake because it has been 2-3 hours. The body does not work like that, and it will also prevent you from looking like 'That guy" remember the body takes a bit longer to digest foods then most people think. Especially given the size of the meal, how much protein you had, and the caloric allotment.
Find the meal frequency which suits you best but don't think it has to be every so often and all the time.
