School dinners, like anything truly evil, inspired a great number of protest songs. By far the most famous of these was the cunningly titled "School Dinners", by person or persons unknown. Sung to the tune of Frere Jacques.
School Dinners,
School Dinners,
Mushy peas,
Mushy peas,
Slimy semolina,
Slimy semolina,
I feel sick - get a bowl quick.
It's too late - I've done it on my plate.
There were a thousand variations on this song, usually stating that the end result of vomit on a plate was indistinguishable from the meal you were served, but this was always the general gist.

School dinners at my primary school weren't excessively evil - provided a pupil had been properly educated about the dangers of Cowboy Hotpot (which looked, smelled and tasted like rotting baked beans) and knew how to avoid the dinner ladies obsession with coleslaw, they could usually keep their insides in.