By Mike Baker
BBC News education correspondent
Should the government double the target for sport in schools from the current two hours a week to four?
There seems to be some tension between government ministries over this. The departments responsible for sport and for health would like to do so, not least as part of the drive to tackle the rapid rise of obesity amongst children.
But education ministers are moving more cautiously. They know that PE and sport face competition for timetable space from equally important subjects, like numeracy and literacy, science, foreign languages, and citizenship.
As ever, the school timetable presents the problems of how to get a quart into a pint pot.
There is no doubt that competitive school sport hit a low-point in the 1980s, largely as a result of the teachers' pay dispute and the reluctance of school staff to commit to after-hours team events. It has taken a long time to recover.
But things seem to be improving with more curriculum time given to PE and an increase in out-of-hours sports.
However, it may seem ambitious to aim for four hours a week when many schools are still struggling to meet the government's target of 75% of pupils spending at least two hours a week on sports or exercise, either inside or outside the curriculum.
Indeed, figures from the Qualifications and Curriculum Authority suggest only about one-third of schools were meeting the 75% target in 2002/3.
On the other hand, the case for action on health grounds alone is strong and would help meet another government target: to halt the year-on-year increase in obesity among children under 11.
Action is certainly urgently needed: childhood obesity rose from 9.6% in 1995 to over 15% in 2002.
Of course, sport and PE are not the only ways to tackle obesity. Better diet, including healthier school meals, is just as important.
Teachers have to use their free time to run teams
But, as a London conference on sport in schools heard this week, exercise has other benefits too, not least the link with educational achievement.
Several speakers noted the rapid rise in academic achievement at specialist sports colleges of which there are now 291 in England.
Although sports colleges tend to serve areas that are more deprived than the average (they have, for example, more pupils on free school meals), two-thirds of them have improved or maintained their GCSE pass-rates since becoming specialist colleges.
Indeed it is claimed they are improving their achievement levels faster than any other type of specialist college.
Queen's School in Hertfordshire, a specialist sports college, is just one example.
Since 2000, its five A* to C scores at GCSE have risen from 50% to 72%, while its Key Stage 3 results have risen every year and its attendance rates have improved.
Of course, some of the improvements at sports colleges may be as much to do with the explicit focus on improvement that goes with achieving specialist status as with any increase in sporting activity for pupils.
But the fact that sports specialists are improving faster than other specialists, albeit from a generally lower base, does suggest some link between sports activity, on the one hand, and improvements in self-esteem, motivation and achievement, on the other.
So, if there is evidence that more sport and PE improves both health and academic achievement, what is holding the government back from requiring more of the timetable to be given to PE?
Some ministers want pupils to double their exercise time
One obvious answer is ministers' fear that it will interfere with their top priority: improving numeracy and literacy in both primary and secondary schools.
Policy-making is all about setting priorities. If you have too many priorities, they tend to all fail.
Schools and teachers already complain about overload. And there are many other lobby groups out there who want more time for their particular subject.
There is, for example, a strong case for making foreign languages compulsory in primary schools.
But how many primary schools could cope if they were told to maintain the push on numeracy and literacy, whilst also boosting foreign languages and finding an extra two hours a week for PE?
But there is another way. The planned growth of "extended schools" could be the opportunity to get more children involved in sport, outside the main school-day.
But how many teachers would be willing to stay on after school to run sports clubs and coaching sessions and to drive teams to fixtures?
Luckily there are quite a few - but are there enough? This is where a change of policy might help.
Should it not be the norm to pay extra to teachers who run after-hours sports clubs and teams?
Or, as some schools already do, at least give time off during the school day to compensate for the hours spent on the sports field?
That way, they would not have to come home late from volleyball club or refereeing the under-13s football tournament only to face a mountain of marking and preparation, as they would have got much of it done during the school day.
Both options, of course, cost money: either extra pay or to fund cover during the school day.
But perhaps this is the only way to find more time for a much-needed increase in PE and sport for many children without further overloading the curriculum?
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