My Junior High school took away lunch hour for some kids. Can they do this?

My Junior High school took away lunch hour for any kid with a zero on any ignment. We have to go into a clroom during lunch and eat without talking at all and work while we eat. we cant even leave the room even if we fill out a hall p. . .i thought that the schools in the state of missouri had to allow us a break sometime during the day. we don't have lunch hour and certainly no recess...so we have no break other than between cles which is to gather out things for out next cl. no break!!! so CAN THEY DO THIS???