I don’t know how it works down there, but one possible explanation is that the kid might have been sent to another high school outside the district for: (1) disciplinary reasons, and/or (2) special education needs.
re: “I don’t know how it works down there, but ...”
Yeah, I don’t know either. Qualifying to attend an out-of-district school (outside of the AISD - Allen Independent School District) is not automatic, it would take some decisions by ‘the bureaucracy’.
BTW, the “Nextdoor” neighborhood ‘discussion’ app is busy with posts about this, and these posts aren’t accessible by the outside public ... nothing revealing posted yet.