I'm with the OP - when I was in elementary school pizza day was maybe 2-4 times per month... there was a "hot lunch" every day, but it was usually burgers, chicken sandwiches, sloppy joes, etc.... I don't think the whole "chicken finger" craze had started yet. Parents were sent monthly menus so we knew if a "good" lunch was coming up. I never particularly cared for the school pizza, as my mother would bring home REAL pizza with the works (SO many meats and veggies) maybe once every month or two, but "icy juicy" day was definitely on my radar!
In Jr. High it was the same food (in fact, everything for the elementary schools in the district was COOKED at the Jr. High), PLUS a snack bar that was open during morning recess and lunch. The snack bar served amazing coffee cake, cup o' noodles, etc. and Taco Bell burritos (bean and cheese) and Pizza Hut pizza (plain or pepperoni) either by themselves or in combination with a soda and chips.... mmm... junk with a side of junk, available every day! (but it's not like they even tried to pretend it was healthy).
In high school, there was essentially only "school lunch" service for those who needed it (and got it for free), almost nobody else ate that food... our snack bar had curly fries, the greasiest chocolate chip cookies ever (oh, they were so good fresh out of the oven, if you had a prep during the 3rd block of the day...), super-fake-cheese nachos, plus the Taco Bell/Pizza hut crap... and we had an open campus, so almost anyone with a car drove off somewhere to get "real" food (but it took the entirety of lunchtime, since lunch was only 40min and nothing's THAT close to campus).
When I was student teaching high school, there was a teachers cafe which had decent food (staffed by students as a "work study" kind of thing) - salads, soups, etc., and the few times I had to eat in the student cafeteria were just brutal... I'm not really sure how ANYONE can think that it's "okay" to have pizza with a side of fries (okay, if you're eating it once in a blue moon, fine, I'll give it to you, but...), also, charging teachers more for the same food and pushing them to the back of the line... yeah, I was glad when the teacher's cafe re-opened. Elementary school lunches where I student taught were no better, though a little closer to what I had as a kid. When I did an internship in a residential facility, the food wasn't TOO bad - real food, which freaked out a LOT of the kids (OMG it's GOAT! I'm not TOUCHING IT!), but also baking (to help with "life skills") and sugary treats more often than I would have liked... When I dropped a bunch of weight quickly through LC while interning and working there, I wasn't really allowed to tell them how I did it, other than "watching what I ate".... *sigh*
So, I guess I went off on a tangential story, but yes, I would consider every week to be more than once-in-awhile, and I would have considered it such before going primal, but as KV8R said, "You don't know what you don't know."
Also props to NowhereMan for this gem: If you eat 20 different kinds of junk food all "once in a while" then you just eat badly. :D
I have a slightly different take on junk food; personally I am against looking at it as treat, which is how pizza served at school is meant to be taken. It is low quality food and I don't associate it with something special. Once kids get that connection junk=treat it's really hard to change that. Look at all the adults that are having a hard time breaking that training.
For third and fifth grade our son went to a charter school 2 days a week in conjunction with homeschooling 3 days a week. They often seemed to use pizza as a reward for something; the kids did well on the STAR tests let's give them pizza. My son never saw it as a reward. He was used to homemade pizza, his favorite was chevre, feta and Parmesan with rosemary and garlic. He's 14 and he still thinks store bought pizza looks greasy and rubbery.
BTW we've been unschooling our son since the fifth grade and we all love it.
The school I work at has pizza every day.