I am another who simply does not get the obsession with hot vs cold food at all, never mind the obsession that anything other than 2 hot meals is not good enough, bordering on neglect. You can be perfectly healthy on no hot food ever, you know!
Well balanced, varied meals of the appropriate portion size is all that matters.
Which is better - waffles and sausage with beans (hot meal) or a cheese and tomato sarnie with fruit, cucumber and pepper sticks, and a flapjack? I know which one I would rather my kids had. I know people who sneer at the "no hot evening meal" families while dishing up nothing but convenience food/junk to theirs!
My DC have packed lunches (as do DH & I most days, sometimes we will grab a pasty or supermarket salad pot). They are generally sandwich based but can also have hummous n veg sticks, crackers and cheese, cold pizza or quiche (both homemade). They have fruit snacks at school and when they get home, and a cooked dinner in the evening. That way I have a realistic idea of what/how much they have eaten.
Our schools dinners are all done in house and are healthier than some, but some parents still have no idea of what was still available when the child got their turn for lunch, how much they were given, or how much they ate.