When second-graders misbehave, my punishment options are very limited.
I can send them to another classroom, but this is an option to use very rarely: it’s only effective in the heat of the moment, it often entails a massive power struggle to get them to go, and it imposes on another teacher. I do it occasionally (and I accept unruly students from other classrooms, to keep my karma happy), but it’s not the best option.
I can give them silent lunch. The unruly kids have a lot of trouble staying quiet during a silent lunch, though. This is nonetheless my most common punishment.
I can give them laps at recess. I also use this one pretty frequently. The law is that they need 30 minutes of exercise, not 30 minutes of free play; if I give them the choice to walk laps by themselves or sit quietly, I’m fulfilling the law. I especially give this one to kids who are goofing around when we’re walking in line, or kids who failed to observe a silent lunch punishment properly (we have recess immediately after lunch).
I can call home. I do this one rarely also, because I want bad-behavior calls to mean something; if I do it too often, parents won’t take them seriously. (There are exceptions: if a parent needs to understand that a certain poor behavior is regular and unacceptable, I might call home every day until they get the picture).
I can refer the student to the office. Again, this is something of a nuclear option: it requires tremendous amounts of time on the part of admin whenever they get a referral, so they don’t want to see them for every minor infraction.
Having the kid stay in the room to do homework is a non-starter: I’m on duty during recess. Having them do it during lunch is similarly unworkable, since second-graders have zero time-management skills and will (I speak from experience here) either not do the homework or not eat lunch. Having them do it at recess won’t work either, since by law they need 30 minutes exercise daily.
One thing I do is a Friday “Ketchup and Relish” period, usually about 45 minutes. It’s indoor play time with good-quality supplies (Lego blocks, checkers, Connect Four, jigsaw puzzles, art supplies, etc.). You can only relish the play time if you’ve done all your homework for the week, plus a random cross-section of classwork that I announce Friday morning. If you haven’t turned everything in, you ketchup during this time, sitting at your seat working while everyone else plays. It’s a pretty powerful motivator, and I have to deal with a lot of tears from the slackers, but eventually most of them get the message and start doing their work on time.