All schools in Britain must check what their new teachers and teaching assistants have done in the past and it's taking longer than they thought.
The checks are carried out with the help of the Criminal Records Bureau (CRB).
It's important schools know if new teachers have ever been caught doing bad things. If so, then that might be a reason for them not to work with children.
The government supports what the schools are doing, but headteachers blame the government for the delay in getting the checks done.