School governors in Wales need to ask more challenging questions of headteachers and look deeper into school results, according to an Estyn inspector.
Governors from schools across North Wales were reminded of their "crucial role" in education during a regional Governors Wales conference in Llandudno.
Mike Maguire, of the Welsh inspectorate, said governors have an important part to play in the self-evaluation portion of inspections and must hold schools to account for standards and quality.
Last year, out of 300 schools inspected by Estyn, 21 governing bodies were given a grade 4, indicating a number of shortcomings.
Mr Maguire said governors often feel unable to ask challenging questions, but for schools to be successful they must.
Assembly deputy minister for skills John Griffiths told delegates that they will be crucial in taking forward massive change in Wales' education system, including 14-19 learning.
Dr Cheryl Morgan, of the Department for Children, Education, Lifelong Learning and Skills, said the co-operation of governing bodies is vital to the success of the school effectiveness framework being piloted in 96 schools.
Governors' role, pages 22-23.