Three years ago, dozens of memory sticks were discovered in a sealed box at a school for children with special educational needs. There was 500 hours of footage which showed children being held in so-called 'calming rooms.' The videos showed the children being hit and denied access to a toilet. File on 4 investigates why a subsequent police investigation and an independent inquiry didn't lead to staff being sacked. File on 4 reveals how staff who were filmed hitting, kicking, and leaving children sitting in urine have not been sacked or referred to the barring service. Reporter: Noel Titheradge Producer: Annabel Deas Technical Producer: Craig Boardman Production Coordinator: Tim Fernley Editor: Carl Johnston