Oh, so what they said wasn't rubbish?
Not completely, but like JFC said, it depends on the area and the schools.
The schools in my city have a school lunch program. There's no cafeteria, students eat in the classroom with their teachers. Like I said, it's compulsory, so unless there are specific allergies, every student eats the same thing on a given day (for example, all school lunches have milk with them, so if you can't drink milk you can opt to skip it.) The teachers usually have the school lunch as well, though they can choose not to get it. It's cheap, easier than cooking and not actually that bad, strictly IMHO. It's varied enough and a heckuva lot better than what I used to have for school lunch in the US.
On some days, particular schools won't get the school lunch, say if an entire grade is on a field trip, so that gets designated a "bento day". Long story short though, yes, there is a school lunch in
some schools in Japan. I'm only speaking for elementary level though, so I don't know how it works from middle school and up.