Supply teachers are having to take on extra jobs to make ends meet and many are considering quitting the profession, it has been claimed.
Campaigners say employing classroom cover through agencies has led to lower pay and poorer terms and conditions.
There are about 4,500 supply teachers in Wales, covering for sickness absence and professional development.
One leading agency denied taking an excessive cut and said it gave teachers "regular and consistent work".
Llyr Gruffydd AM, Plaid Cymru's education spokesman, said he had been…