That's a big issue with students. High schools, unlike, colleges and jobs, can be pretty dang strict about eating during non-lunch time, and many don't have access to microwaves.
When I was in high school, we didn't have access to any microwaves. On top of that, assuming some teacher didn't decide to be an a*s if they saw someone eating in the hallway between classes, we had 5 minutes to get our stuff, and get to the next class - so eating in between was next to impossible anyways.
That wasn't an issue for me then, since I wasn't worried about fitness at the time. But I can remember how impossible that would seem.
I think it's a good idea to get your meals equally spaced and equally divided throughout the day, but we also have to balance what is ideal with what is realistic. If you eat breakfast before, lunch during, a "meal" when you get home, and then dinner - that's 4, not horribly unevenly spaced, meals. That should be fine.