While I haven’t heard of any instances of students doing this for additional academic challenge, I have heard of it happening because a kid encountered disciplinary trouble, because they did an activity outside school (often sport at elite level ) that either required they be closer to home or coach or switch from a 6 day schedule to a 5 day one, because they were being bullied or otherwise socially tormented, or because they were academically drowning and needed a school with more support.
I would not advise judging any school on its first semester – many deliberately tone it down until expectations are fully understood and to get those from weaker middle schools placed properly, realizing that being away from home is a big adjustment for most.