A lot of that is different accounting.

In most US states, schools are nominally independent bodies of government, they carry all of the costs of facilities, pensions, etc. They also need to comply with all sorts of cost enhancing building and labor standards.

So in my city, the school collects $28k/pupil. That includes something like $150M in debt for buildings, salaries, 20% of salaries for pension obligations, 15-20% for employee healthcare, key expenses for the various charter schools, etc.

They also need to deal with compliance issues. Because some redneck place in Mississippi would give poor kids a slice of Bologna and stale bread, there are prescribed calorie and nutrition standards that get audited. So you can't prepare fresh foods.