More pupils from low income homes in England are to be offered free buses to school to stop transport costs pricing them out of popular schools.
Ministers say they want all parents to be able to exercise choice
Some 135,000 more secondary pupils will be offered free travel to schools two to six miles away, ministers say - and up to 15 miles for faith schools.
It is hoped the move will widen choice for parents put off more distant schools by the extra travel costs.
All pupils travel free to the nearest suitable schools over three miles away.
The detail of the plans mean that from 2007 more disadvantaged primary school pupils will get free travel to a school closer to their homes, two miles away rather than three, but no more than six miles away.
From 2008, an estimated 135,000 children on free school meals will be offered free transport to one of three nearest secondary schools within a two to six mile radius, the Department for Education and Skills says.
And some 14,000 disadvantaged pupils attending faith schools, which tend to have larger catchment areas, will get free travel to schools between two and 15 miles from home, it is estimated
The DfES says children pay an average fare of £7.29 a week - a cost which can hit low income families hard.
But it has been unable to explain why it is changing the mimumum qualifying distance on a means-tested basis - so a poorer child will get a bus to travel two miles to school whereas a better off child will be expected to walk three miles.
In a statement, Schools Minister Lord Adonis said: "We want to remove transport as a barrier to parental choice.
"No young person should be prevented from going to school of their choice simply because of travel costs.
"That's why it is vital to expand the right to free school travel for young people from low income families to give them real choice in applying for schools."
The DfES says a survey showed four of out of 10 parents living in social housing cited travel convenience as the most important reason for choosing a school.
Only one in 10 children entitled to free school meals travel three or more miles to school compared with 18% of children not from low income families.
Liberal Democrat education spokeswoman Sarah Teather said: "This may offer greater choice to some families but the fact remains that parents would always prefer a good local school for their children over a long bus ride to reach a satisfactory one miles away."
US-style yellow bus school transport schemes are also to be piloted in England from next year, the government confirmed.
It is investing £21.4m in 20 local authorities which will transport pupils to one of three nearest schools, under pilots that will run until 2013.
A DfES spokeswoman said: "There will not be any decision made about the national picture until the schemes have been evaluated."
Part of the reason for this is that local authorities in urban and rural areas will need to provide different schemes, she added.
The scheme, which aims to cuts school-run car use, will use a "mix of free, subsidised and charged-for arrangements".
Local authorities will be able to charge up to £1 a day for the transport.
The plans were announced in the education White Paper in 2005.