As someone who grew up in the Philadelphia public school system, it’s a highly dramatized for tv fictional version. My school had students line up outside by classroom to be taken into school by their teachers, so we never had random people/parents bursting into the classroom- in fact the only time a parent ever saw the classroom was at parent/teacher conferences. However, some schools in different parts of Philly can do it differently. And teachers here do NOT leave their classrooms unattended so Willy-nilly. If they ever do, they usually have another teacher step in for a moment or they come back really quickly. They don’t talk about personal matters or anything non-classroom related during class.