Parents - just say no.
"In a secondary school you have around about a 25-minute period to serve potentially 1,000 pupils"
That's 40 a minute, 1.5s per pupil. Sure it's pipelined, and possibly superscalar, but this seems mad.
Yeah, because the combined brainpower of an entire nation of teachers hasn't worked out that they could simply stagger lunch 'hour' by a bit to create a 'lunch 2 hours', or at least extend the serving time to 55 minutes (+>100%) with a 1hr 30 window, with some years teaching over the first or final 30 minute period.
Sure, logistics of teacher availability (they need a break too) and in secondary schools they teach all years, so the classes still teaching whilst other years are eating, then the eating year needs to come back into class, but the teacher needs a break, that's a difficulty, I can't see how it isn't solvable.