Moves to reinforce a ban on all formal breaks except lunchtime in one US city’s primary schools have left local teachers fuming.

The law reflects a broader trend sweeping schools in the US towards dropping playtime from timetables to cram students for high-stakes tests.

Education chiefs told primary school headteachers in Tacoma, near Seattle, late last month, that “with time becoming more precious than money these days... there are to be no scheduled daily recesses... we need to reclaim as much time as possible for instruction.

“Lunch breaks can include outdoor playtime, but should never exceed 40 minutes.”

Nursery teachers were allowed to “engage in well-organised and supervised developmentally-appropriate, gross motor activities for one 15-minute period per day”.

The memo reiterated a policy first announced in 1997, amid reports that some local schools were ignoring it.

But it has left many staff incensed, according to Gayle Nakayama, president of the local teachers’ union, the Tacoma Education Association.

Tacoma is not alone. Four in 10 US education authorities have shortened breaks, eliminated them outright or are considering plans to do so, said Dr Rhonda Clements, president of the American Association for the Child’s Right to Play.

The trend reflects the pressure schools face under the academic accountability regime established by the Bush administration’s No Child Left Behind Act. This penalises them for missing test-based performance targets, and similar local initiatives, said Georgianna Duarte, professor of early childhood development at the University of Texas.

But eliminating breaks may be counterproductive, warned Professor Duarte, who said children were less receptive to instruction if they were not allowed to take breathers.

At Tacoma’s Whittier elementary, whose use of breaks helped spark the official memo, teacher Rachel Lovejoy said her six-year-olds were often “cranky” without playtime.

Ironically, Whittier boasts Tacoma’s best mathematics and writing test scores. Playtime does not take away from academic learning, but is part of it, said Ms Lovejoy.

Unstructured free time promotes creativity, social development and higher-order thinking, added Professor Duarte.

But breaks can be distracting, said Patti Holmgren, of Tacoma’s education authority. “Time on task produces results, and every minute matters.

“We’re not chaining pupils to desks,” added Ms Holmgren, who said staff were free to allow time-outs if they felt children’s concentration wilting.

Bucking the trend, Michigan, Connecticut and Virginia recently enforced breaks in their schools. Partly driving this is concern at mounting childhood obesity. The proportion of overweight adolescents in the US tripled from 5 per cent in 1980 to 15 per cent in 2000, with inactivity cited as a major cause.

US primary schools have the world’s longest teaching hours - 1,139 hours a year compared with 617 in Japan, for instance - according to Organisation for Economic Co-operation and Development data released last month.

Researchers in the UK found that shortening school breaks undermined children’s social relationships and long-term emotional development. Dr Peter Blatchford, of London university’s institute of education, said schools often do not recognise the social and educational value of undirected free time.