Do some searches for quinoa salad recipes online. Quinoa is a complete protein. It's a super food! Kids tend to be picky so you will have to tweak it for your child. Make it up. If he she likes rice/pasta, quinoa is a great choice because it doesn't turn straight into sugar like rice and pasta. Maybe put in some natural ham cubes, cheese, veggies, lemon juice, olive oil, etc. I've never done this but try making it like mac and cheese? Or add pasta sauce and homemade meatballs. Get him a thermos bowl (don't buy the ones that are plastic on the inside, spend a little extra and get all metal). Our kids don't need plastic chemicals leaking into their foods. I think Coleman makes one for about $20. Does he like soup? What about homemade chicken tenders (cut them in strips, dip them in a blend of melted butter and honey (or just butter). Dredge them in plain raw oats that you have blended up in the food processor with some salt and spices). Pan fry them (if they are getting too brown and not cooked inside, throw them in the oven for a bit). This requires a little work so I tend to make a bunch and freeze the leftovers between waxed paper, then thaw them out and heat in a toaster oven for dinner. Maybe you can toss it right into a box and it will be thawed by lunch time. Can he have ranch dressing? I'm a huge fan of everything homemade. Much better for our sensitive children. He might like it better if he can dip. What about Applegate brand hot dogs? Or just plain meatballs in homemade pasta sauce?
Tuna/Chicken salad with sides of celery, carrots, cucumbers, etc. Your best bet is going to get him to learn to love quinoa. It will be a good substitute. Your whole family should be eating it. Great food.
Boiled eggs make for a good lunch. Or, deviled eggs, He might not like the pickles. Leave them out, if so. Hummus and veggies or take a whole wheat tortilla, spead it with hummus, roll it and cut it into sushi rolls. Check the ingredients though (or make it homemade). Not sure if the kid in the class is allergic to seeds (the tahini in the hummus). I make a black bean hummus that is really good and my kids eat it too.
What about beans? Can he have complex carbs? Does he like beans? If he can have the whole wheat tortillas (like I mentioned above) make quesadillas with refried beans and cheese. Those are good cold too. Hopefully this gets you started. We are dealing with food restrictions as well. It makes life MUCH, MUCH harder!!!!!