How the m other lot live, eh?!
Having attended one of said "private boarding schools" for 5 years (not as a result of family wealth - it was paid for by my dad's job as a perk (??) for living abroad) I can categorically say that the catering at my particular school was utter shyte. And I mean REALLY shyte.
e.g. A typical day... Breakfast. Bowl of corn flakes with 2 pints of milk to share between a table of 8 people. Followed by ONE morning roll with a sliver of butter, in which you could put (if brave enough) marmalade. The cheapest type of marmalade from a huge catering tin, which was put into smaller dishes and which stayed in said dishes for the rest of the school term.
Lunch.... Small portion of "stew". Lucky if you found any meat in it, basically watery gravy with veg.. Served with mashed potato (instant smash, not real potatoes). Pudding of steamed sponge and custard.
Dinner.... Watery "soup" (packet soup using far too much water). Main course... Beans on toast. And not a lot of beans, maybe 3 tablespoons. No pudding.
Forgot to mention our breaktime "treats" mid morning and afternoon. 2 digestive biscuits.
The choice was, as always, take it or leave it. I could go on about the boarding school experience for days, but suffice to say if you think that is "how the other half live" you really don't know much about it*. It was so bad that I actually used to look forward to the airline food on the way home at the end of term. That was the only perk; holidays in Jamaica. In the 70's.. Loved that, but then I had lived there full time and gone to school there for 5 years prior to being shipped off to the ar$***le of the universe, supposedly for a better education. It wasn't. I sat bored for the first year as I had already covered everything (apart from British history, which bored me shitless anyway after learning about West Indian history) at school in Jamaica.
I left that asylum as soon as I could, 2 weeks after I turned 16. Weighing 10½ stone at a height of 5'11". Most likely malnourished too. I joined the Merchant Navy and could not believe how well fed we were. Others thought it was normal, but it was luxury to me!
*I am not disputing your story. But I knew people from other boarding schools who were in pretty much the same situation as I was. No doubt though, there were better boarding schools in existence, somewhere. If the care commission had been in existence back in the 70's things might have been better. They would have closed down that dive for sure.