text: Chief inspector of schools Meilyr Rowlands told AMs it was partly due to the "unintended consequences" of how schools' performance is measured.
  Another Estyn witness said more able learners' progress had been "stifled".
  Ministers agreed they needed "to do more to push our most able students" and were introducing changes to raise standards "for all our young people".
  The Welsh Assembly's Children, Young People and Education Committee was quizzing Estyn about its annual report, on Wednesday.
  Mr Rowlands said that schools focused on a performance measure which requires pupils to get five GCSEs at grade A*-C, including English or Welsh and maths.
  That, he said, encouraged schools to focus on the borderline between C and D grades "and possibly not giving enough support for those who could get As and A*s".
  But he said that evidence from primary schools, further education and the PISA international tests also suggested that able and talented pupils were not given enough support in the education system.
  "I don't think schools and the education system more generally have done enough," he said.
  Claire Morgan, Strategic Director for Estyn, said the focus on particular performance indicators meant there is "some gaming, [and] early entry that hasn't helped to stretch the more able".
  "I think this has stifled the progress of more able learners," she added.
  A Welsh Government spokesman said ministers recognised "we need to do more to push our most able students to reach their full potential".
  "Through programmes such as the Seren Network, we are already supporting our brightest students to reach our leading universities.
  The spokesman said changes were being introduced to the system used to measure schools' performance for 15 to 16 year olds, following a review of qualifications for 14 to 19 year olds.
  The changes were intended to "raise standards and extend opportunities for all our young people no matter what their background", he added.
target: More able children are not getting enough attention in Wales' education system, the schools watchdog has said.