I'm 57 so went through the evolution of school dinners.
Primary there was one dinner and one pudding and you had to eat it. I went to three different primaries and that was the same at them all.
Sometimes it was good, others, not so. Second primary did spam fritters on a fairly regular basis that I hated and at school 3 there was a weird stew they served with a slice of pastry, we all called it spew.
That school also served milky coffee in the winter.
At secondary we got a choice of two meals and two puddings, still meat potatoes and 2 veg type meals.
Then the rules changed and we got a choice of the main meal or 'soup and a sandwich' which was actually a fairly decent meal. No I didn't grow up in Ireland but the school was run by Irish nuns.
When I got into my final year it changed again and it was basically 'chips with everything'.
We also had a couple of students who went home for lunch.
I actually think the soup and sandwich could work for a lot of children. Hide the veg in the soup and have an assortment of sandwiches / rolls / baguettes.
We need a total rethink. Food should be something that contributes to education. I did supply at one school that had a French chef and compulsory (free) breakfast - you didn't have to eat but you had to go with your class to the dining area.
Classes were often a nightmare before breakfast, mainly due to students wanting to know what time breakfast was that day.
Breakfast was porridge or cereal, beans on toast, spaghetti on toast (tinned stuff) hot and cold drinks.