Charging is just one option in a range of initiatives

They have confirmed they will introduce legislation for England as soon as parliamentary time allows.

Up to 20 local authorities will get up to �200,000 apiece to develop "greener, safer and healthier" travel schemes.

Under the current system, travel is free for those who live more than three miles from the nearest suitable school (two miles for those aged under eight).

Pupils living within this distance usually have to meet the cost of getting to school themselves. Those outside get the whole journey paid for.

'Confused'

The latest developments are in the government's formal response to an education select committee report on their draft proposals.

The committee had said the government seemed "confused" about its plans. Encouraging pupils to walk to a local school seemed to be at odds with giving people a greater choice of schools.

And the MPs said charging people for home-to-school travel that was currently free might prompt more of them to take their children by car.

The Department for Education and Skills says the impact is likely to depend on quality of service - and will be monitored closely.

It does not accept that parental preference is incompatible with improvements in school transport.

Options

Ministers stress they are not saying there should be charging - it is up to local authorities.

Pilot schemes they are keen to see include:

• more "high quality" school buses with CCTV and well-trained drivers, with extra buses to cover after-school activities
• "walking buses" where volunteers escort pupils to school in groups
• safe cycle routes with secure bicycle storage at schools
• staggered starting times for different schools in an area - to cut traffic congestion

A survey published by the department suggests the average paid by parents whose children do travel by public transport, school bus or taxi is �7.29 a week.

The small survey also suggested people on lower incomes were more likely to pay fares - but 47 of the 318 polled declined to disclose their family incomes.

"The present system is unfair because it is based on the distance pupils live from school and not parents' ability to pay," said the Education Minister Stephen Twigg.

Exercise

Twice as many children were driven to school now than 20 years ago - around 40% of primary pupils and 20% of secondary pupils.

"Most of these journeys are less than two miles, meaning decreasing numbers of children walking or cycling with serious health implications in terms of lack of daily exercise and the growing proportion of children who are overweight," he said.

"That is why we want to encourage local education authorities to make walking, cycling and bus travel safe, green, healthy options for more schools and their pupils."

Recent research has indicated that, in terms of children's overall exercise, a walk to school has only a marginal impact - but officials argue that every little helps.

The NASUWT teachers' union said any changes needed careful consideration to avoid replacing one problem with another.

"For example, staggering school opening hours to ease traffic jams could cause havoc for parents who have to drop off their children at different schools on the way to work or for teachers and their childcare arrangements," said the acting general secretary, Chris Keates.