damn, my taste buds have good memories of all these things. mouth is watering reading about them.
when I was little, my mom actually worked for the schools, which allowed her to purchase the food in bulk... so I ate those rectangular slices during summer too. cooking them from unfrozen in a toaster oven.
I actually remember only being allowed to buy lunch one or two days a week, I brought my lucnch. but thursdays was always hamburger or vegetable soup/grilled cheese. and sometimes they got the grilled cheese just perfect.