My favourite used to be chocolate sponge with mint custard, it was fantastic, I always enjoyed my school meals in the 70's & early 80's.
I was a school cook 10 years ago, in the days before Mr Oliver & his ideas, we made everything from scratch, and we also catered out to 2 other local primary schools, we made samosas, veg curries, all our own bread for sandwiches and pizza bases. Spag bol etc.Vegetables were a plenty in various disguises. There was nothing unhealthy apart from the once a week we had to serve chips. We had a very high uptake of kids eating the meals, including my own three kids who loved it as it was like eating what mum made at home but with pudding.
Even then the puddings were the most popular thing, rice pudding was extremely popular as were all the sponges and custard, least popular probably jelly & yogurt. We also made brownies & cakes full of fruit & goodies which they could buy at break. But no doubt under these new healthy eating rules these ideas will all be gone.
My two kids still at school take sandwiches & have done for the past 2-3 years as they don't like what is served in school, their lunch boxes are full of homemade creations that they love.