Our local ps offered what ever classes my ds were interested in (sports, shop, etc.), even if that meant they weren't full time ps students. The ps was just happy to have them attend and get the tax dollars.
I wouldn't say "never" because I think totally denying a child something makes them want it more. We've always done our best to help my SD see WHY we chose the things we do. Right now her mom has told her that she will only homeschool when she is younger but "of course" she's going to want to go to High School so she can go to prom (? What does a 7-year old know or care about prom?) So she has it in her head that she will be going to high school. Her father and I are more against high school than grade school due to the drugs and peer pressure. We are working very hard to instill very good morals. We hope she grows up dressing modestly, using appropriate language, having manners and genuinely caring about others. Already she is starting to spot teens who make poor dressing choices. She knows drugs are bad, and we have education set out for that later on. We realize if we truly do our job as parents and step-parents when she is young she will know how to study and learn on her own. She'll make good choices. In that case, High School may be fine if she so chooses
I think I would say not in the middle of a school year. I'd make them at least wait until the beginning of the year and hopefully by then they'll have changed their mind. In the time between that and the new year I'd work on finding out what it is they are seeking in going to ps; If it's more friends or activities you can work on giving them more of that. My son is only 7 but had a similar thing, declared that he wanted to go back to school....turned out it was just because he missed being around other kids, so we upped that and he's fine now. Best of luck with everything!
I think you're right. Its just hard at the middle school age. Kids aren't as inviting as when they are younger - they have already formed their social circles. My daughter made a lot of friends with nice girls in school last year but they are busy with activities (normal overload) and don't have time for anything other than those. That means my daughter thinks the only way she can be friends with those girls is to go to school and join all the activities. She isn't used to that pace though so she probably wouldn't deal well with that for long.