This seems to be a rather popular topic amongst the teenagers who don't really know anything, but I'm sure there are some points that may be correct. There's a very common idea that a school is very much similar to a prison, systematically. A few points were brought up by my Aunt over a somewhat bias facebook post (She's homeschooling her children, and hates the public school system). She brought up a few similarities between the system that public schools and prisons have. These may or may not be valid, that's why they are up for debate.
1. They both have an authoritarian structure
2. They both have strict dress codes
3. They both have "Negative" reinforcement
4. "Walking in lines" honestly this one is pretty fucking stupid
5. Abridged freedoms
6. No input for decision making
7. Set times enforced for eating, walking, etc.
Here's a few articles I briefly skimmed through that bring up some points.
Debate.