Education Secretary Ruth Kelly has said it would be for schools to volunteer to take part in Labour's plans for more out-of-hours activities.
Children might take part in musical activities
Providing "extended schools" would be a duty on local education authorities, she told a news conference.
Teachers would not have to run the clubs, she stressed. Unions have been concerned about funding and workload.
Ms Kelly said that a re-elected Labour government would spend £680m getting the scheme started around England.
She told journalists one block of £250m over the next two years would be spent on the idea.
Answering questions, she said this was in the Budget last month.
In Gordon Brown's Budget speech it appeared to be something different.
"No direct payments to school head teachers existed in 1997. Today the typical primary school receives £30,000, the typical secondary school £96,000", he said.
This was "money direct to the school and the head teacher to spend on the school's priorities".
He then said these payments would rise, to £36,000 for a typical primary school and to £115,000 for a typical secondary.
But a Labour spokesman pointed out that the full Budget document had said this extra was specifically "to help schools meet the challenges that provision of extended services involves in the shorter-term".
Duty on authorities
Ms Kelly also told reporters there would be another £430m, between 2006 and 2008, if Labour were re-elected: "new money, that we are allocating now to extended school provision".
This would involve people such as parents' groups, charities and voluntary organisations doing such things as homework clubs, music, drama, dancing or sport.
"Schools are simply too important a resource for local people, to stand idle at the end of the school day," she said.
Asked who would run extended schools, she said "we are not talking about teachers - this is not something extra that we are imposing upon them".
It might be, for example, a French assistant taking a French group or a university teacher running a science club.
It would be "an explicit duty on local authorities" to secure the necessary facilities.
"They will want to work with schools and it will be up to schools to volunteer for that," she said - perhaps working as a group locally to offer a range of clubs.
But if they chose not to, it would be up to the local authority to find other providers.
The pledge was that all children would have access to the activities - "no more latch-key kids" - rather than that all schools would offer them.
The Liberal Democrats also support the idea of an extended school day - provided the responsibility for co-ordinating and managing it falls to the local education authority rather than "already overworked head teachers".