I didn't have primary school dinner as it was only a 10 minute walk from home. We did get those small bottles of milk at morning break, however.
At secondary school, dinner was mayhem. You had to buy dinner tickets a term in advance at the Porters Lodge and then cash them in on the day. Tables were arranged in "houses" with a raised table on a dais for the masters. Prayers were said before the kitchen doors were ceremoniously flung open and teams of charioteers pushing trollies, two for each house, roared out into the main hall like a Formula 1 Grand Prix start. No trolley was overturned to my knowledge, but collisions were frequent. There was a roster for trolley-pushers which you were put on, possibly as punishment duty. Any trolley that made it out of the door late for any reason, i.e. slow to be stacked up in the kitchen, was greeted with scorn when it eventually arrived at the house table.
Anyway, that was where I fell in love with plum tomatoes. I'm still passionate about them today! It was the only thing to make palatable and help down the strange-tasting mashed potato and brown meat from some dubious source, anything from aardvark to zebra for all we knew.
Puddings were very often one of those very small, round, tube-shaped ice-creams which came in a sort of paper wrapper. Otherwise it was something and custard.
I abandoned school dinners as soon as I could. There was a healthy black market for unused tickets, a good way to make some extra pocket money on the side .....