You can report a teacher for serious misconduct to the Teaching Regulation Agency (TRA). You should follow the school's complaints process before reporting a teacher for serious misconduct. Your report may not be investigated unless you do.
Call the local school board or the truancy Dept. There are laws about attending school and they may take it more seriously than CPS.
Children who are on roll at a school but are not in regular attendance. In this case, referrals should be made to the Education Welfare Service, or the school's Attendance and Welfare Officer.
Under common law, even minimal force can count as assault if it's perceived as unlawful and unwanted. Therefore, pushing can indeed be classified as assault, especially if it leads to a complaint or charges.