The food at my primary school (early-mid 90s) was great. Home cooked, not a huge amount of choice/variety but tasty and filling. There was always a queue for seconds!
Secondary school was rubbish in comparison. I lived off chips, cheese and gravy for three years. They actually sold Pot Noodles when I joined in Year 9!
The food at the (independent) school I work at is phenomenal. Every day they offer:
Baked potato, baked sweet potato, or pasta with cheese/beans/tuna/two sorts of topping (e.g. vegetables Provençal or Moroccan lamb)
Vegetarian main
Meat main
'Street food' (e.g. jerk chicken or jerk aubergine - always a vegetarian and meat option)
A full salad bar
A hot pudding
Yoghurts
Fruit (apples, pears, satsumas, plums, pineapple, melon)
Jelly
Tray bake (flapjacks etc)
That said, the number of kids who just have plain pasta with cheese every day is depressing. I eat like a king, though!