80% 'learn less' with supply teacher - survey for AMs
More than 80% of pupils in Wales say they learn less when they are taught by a supply teacher.
Nearly a quarter of children reported being taught by a supply teacher every week, in a survey for assembly members.
One inspector said every school they spoke to could give an example of a supply teacher being asked to leave due to concerns about their work.
In Welsh-medium schools nearly half of pupils said they were taught in English when supply teachers took lessons.
The problem stems from teacher absence in Wales - with nearly 10% of lessons being covered by supply teachers.
Nearly 1,000 pupils took part in a questionnaire for the Assembly's education committee, which is looking into the supply teacher issue.
Catherine Evans, an inspector with Estyn told AMs: "Every school was able to give an example of how they'd had to ask someone to leave and not return to work at the school.
"And in those examples it wasn't anything serious enough to have to contact the General Teaching Council for Wales (GTCW) or go down that kind of route. But they were serious enough to cause enough of a concern that they didn't want those people to return to work at their school."
She also conceded it was possible those supply teachers could continue to work at other schools.
Ms Evans said there were also questions about the quality of the teaching which emerged from some of the responses to the questionnaire.
"Sometimes pupils worked on paper, and that work then wasn't marked it just seemed to disappear into the ether," she said.
"They sometimes undertook tasks like watching a film or a word search and that didn't always connect with their prior learning."
There is also a concern about a lack of training.
Estyn's incoming chief inspector Meilyr Rowlands said: "The bottom line is money.
"All of those things [personal development training] would cost and I don't think anybody wants to pay - the schools, the local authority or the agency don't want to pay for developing supply staff and supply staff themselves don't want to give up a day."
The committee's inquiry will be looking at all aspects of how supply teachers are used and monitored and the impact on pupil performance.