As a student who grew up attending Massachusetts public schools, this is fantastic news. Just wish that could have been me!
I used to bring a lot of boxed lunch in most days instead because school lunches were an unnecessary expense, but sometimes I'd buy school lunch if it was one I liked.
I don't know if this applies everywhere, but my school district at least had a needs-based free lunch (and breakfast) program for those from low income families, but honestly all students deserve to eat a healthy and nutritious meal during school, which I am sure also takes quite a bit of stress off of parents.
The trouble with needs based programs is that students who receive the free lunch then get shamed by other students for being poor. Thus the movement to give the lunch to everyone. The cost per student is fairly low compared to the other expenses of running a school. Plus there are savings resulting from getting rid of the bureaucracy that figures out who is needy enough to get a free lunch, getting rid of the payment collection operation, etc, that partly offset the cost of the additional free lunches.
It depends on how you manage it. We had a system where parents could pay up front for your lunches, and students using that system got their lunches the same way the needs-based students did - the lunch lady just checked their name off the list for the day. You could guess at who had which, probably, but there was no way to confirm it.
That being said, you're right about the bureaucracy and I'm all in favor of free lunches for all students regardless of their parents' income.