THis is a specialty program WITHIN a normal school. The rest of the students are part of the normal school, and don;'t need special language. By putting the specialty school in a normal school, the specialty school kids get to take classes (like gym, art, music) with the other students for assimilation, but can have one or two teachers who know their language to help with the science/math/english/history courses.
That's why the kid used to go to the school, it was his normal school until the parents moved out of the school's boundary. Often school systems will allow kids to continue attending the same school in that situation, but require the parent's to handle transportation. IN this case, the specialty bus stopped near their new house, so the parents asked for, and got permission to, put their kid on the specialty bus (I think -- or maybe they just did it without permisssion). One day the school decided not to let the kid use the bus, and they forced the kid to stay at school and called the parent, which led to this story.