Aside from the fact that this would never actually happen. Who in their right mind would put it in a letter asking parents to please make sure their kids attend classes...?
Oh and if they do walk out, which they often do, getting sent to an actual cell for up to a year (mostly -thank god- 2 weeks) is the normal reaction. I'm not sure if those qualify as juvenile hall -they probably don't- but they certainly are cells.
CPS can do whatever they want to a kid. The kid "is not being convicted or punished" (just incarcerated and ripped from their environment, sometimes for decades), just "protected", so none of the normal protections apply. Often one has the clear impression that kids are imprisoned, not because of any problem with the kid or parents but because some CPS facility has a quota to meet (X children "helped" or no more subsidies). I even found an article that said judges felt pressured to lock children up because otherwise the closed facility claimed they would go bankrupt and the judge would lose the possibility of sending anyone there.
This is a problem because juvenile delinquency is and has been dropping like a stone for decades now, so those facilities have an ever smaller share of actual juvenile offenders, and a large majority of kids where some CPS worker (an individual) decided they needed help, and mostly the kids and parents refuse, of course, because these facilities are not seen as any kind of improvement for problems (and of course, they aren't).
Please don’t laugh things away because you think they don’t happen.