If he eats a full dinner I call it good.
My Son never ate anything that I sent and barely touched School Lunches, so I started giving him a quick breakfast (Oatmeal, Breakfast Bars. and a Protein Drink/Shake) and when it was dinner time I made food that He'd surely eat.

I’ll stick cold pizza on an ice pack in his lunch and he will eat that sometimes. He prefers pizza with no sauce. The croissants have fat and calories in them so that’s good. Get permission from school for him to be excused from balanced meals, you don’t want them forcing him at meal times it might make him regress or traumatize him. They need to be respectful of his eating habits.

I forgot to mention I pack a balance of healthy and not so healthy food in my son’s lunch bag. Most days he brings back the extra snacks he didn’t have time to eat. So when he gets home from school, he will have a fruit by the foot or a pudding cup, for example. So I am assuming they don’t want him to have too many sweets during the school day because then he won’t focus on his school work.

And that's what matters, he's healthy.

That's what we are pretty much doing. We give him a shake, a vitamin and his medication. Some french toast sticks(have to be the great value ones) and when he gets back y try to fill him up with what i can. He has been healthy so far and he recently gained a pound, so doctor was very happy.