Most primary schools in Wales are failing to challenge and stretch their most able and talented pupils, according to a critical report from Estyn this week.
The inspectorate says schools are not doing enough to identify, support or track the progress of the highest-achieving 20 per cent.
Challenging more able and talented pupils is a top priority for the Welsh Government, but chief inspector Ann Keane says it is often a "weak area" in primary schools. Estyn also raised concern over the issue in its last two annual reports.
Estyn found that in key stage 2 the proportion of more able and talented pupils achieving above the expected level fell between 2004 and 2010.
Although the percentage of pupils attaining level 4 and above in English, Welsh and mathematics increased in that time, the percentage of pupils reaching level 5 or above decreased in all subjects.
Very few pupils achieve level 6 in one or more core subjects and it is extremely rare for pupils in Welsh primary schools to attain level 7. However, in England attainment at these higher levels is improving.
Wales has few high-achievers compared to the top-performing countries in the world, and the report highlights a number of schemes being trialled in other European countries that it says "provide pause for thought".
These include more autonomy for schools in Belgium and specialist schools for the most gifted in the Netherlands. Inspectors found that able and talented pupils are more likely to achieve high standards when schools identify them accurately, set targets and track their progress.
Estyn also highlights the considerable variability of support given by local authorities across Wales, and says school improvement officers often have limited resources to help schools improve achievement.
Anna Brychan, director of heads' union NAHT Cymru, said: "Our members will recognise a picture that shows variation in practice across Wales. Local authorities as well as schools will need to look at this to try to achieve a more even pattern across the country so that more can perform on a par with the best.
"In the end, though, this is probably the result of the fact that our system is largely crafted to bring up the bottom rather than stretch the top."
Among its recommendations, the report says schools should provide more "challenging and individualised learning experiences" to help more able and talented pupils achieve the highest standards.
It also says there should be training for school leaders, teachers and support staff.
A Welsh Government spokesman said the school effectiveness framework aims to ensure that all pupils are supported to reach their full potential, including the most able and talented.
He added: "The new school standards unit will be looking at performance across the ability range, with a focus on the effective use of data to identify strengths and weaknesses and target effort and resources."