I just wrote an entry about kyushoku, or school lunch, on Higo Blog. I would have to say that the school lunches that I had in Ubuyama were much better than the school lunches back in SoCal, but you can't really compare soggy burgers wrapped in foil paper to rice and a broiled slice of mackerel. Then again, in high school I could buy personal pan pizzas from Pizza Hut. Those pizzas were about the same size as Japanese pizza, more filling, had real pepperoni and sausage (instead of this mayonaisse and corn bullshit! WTF is up with that???), and cost only 3 bucks!
The worst things about school lunch in Japan that I have experienced:
The small candied fish served on top of rice.
Liver stew.
Pickled hotaru ika (firefly-squid).