Inspection reports of the 99 schools announced last week show poor teaching is rare. Just three schools in available reports had a lesson marked at grade 5 - the lowest possible - but most have a majority of grade 2s to their credit.

Most already meet the Assembly government’s target of 98 per cent of lessons at grade 3 or above for 2010.

Several are showcase establishments with a string of seven grade 1s, but most are middling with a mix of grade 2s and 3s.

However, there are wide variations between schools and classrooms of similar free school meal (FSM) uptake. Treorchy Comprehensive, for example, was awarded seven grade 1s in its 2006 report.

With 21 per cent FSM uptake, subject achievement at grade 1 overall was 15 per cent. Top-grade teaching was 27 per cent.

But at Heolddu Comprehensive in Bargoed, with FSM uptake at 25 per cent, 10 per cent of subject achievement was grade 1, along with just 8 per cent of lesson quality. The school was awarded six grade 3s and one grade 2 in 2005.

Wales has been carved up into four regions to trial two approaches under SEF this September. Superheads from high-performing schools will be drafted in to help raise teaching practice in the North and South East. In the South West and Mid Wales, SEF will be delivered through local authority-led consortia.

The school with the highest percentage of grade 1 lessons is Penybont Primary in Bridgend. Head Chris Britton is one of five working for the Assembly government on delivering SEF in schools.

Speaking at a visit to pilot school Dinas Powys Infants, education minister Jane Hutt said: “For too long our classrooms have been islands of effective practice.”