By Hannah Goff
BBC News, at the NASUWT conference
Parents could dump their children in schools from dawn until dusk under plans to extend their opening hours, a teachers' union conference has heard.
More schools are offering after-school care
The government's policy of opening schools from 0800 to 1800 risked damaging family relationships, head teacher Stuart Merry told the NASUWT.
Mr Merry, from Kirklees, said schools should not encourage parents to be away from their children for long days.
Conference delegates said extended
schools should not mean extended hours for teachers.
Mr Merry said some parents regarded their children as "accessories" to their busy lives and left them with childminders for up to 12 hours a day.
He acknowledged some children, especially from deprived backgrounds needed help, but said that should not be done on the "backs of teachers".
He said: "They are actually better off being with someone who's qualified, getting a decent breakfast so they're ready for school and having some care afterwards."
"But I know children who are left with childminders at sometimes seven and eight in the morning who don't see their parents until half past six or seven at night.
"It's not a real issue for them to make a cohesive family.
"Some people will just see this as another way of dropping off their children so they can get on with their busy lives.
"I don't like that at all and I don't think schools should be in the business of encouraging that."
NASUWT General Secretary Chris Keates said some people had no choice but to go out to work.
She added: "For some children, particularly those at risk, giving them wrap-around care gives them extra support."
Delegates backed a motion calling for union officials to ensure that extended schools did not mean extended hours for teachers.
A Department for Education and Skills spokesman said extended school activities were voluntary and provided "a safe place for children to be".
He said: "Extended schools also provide parents with greater choice, flexibility, convenience and accessibility in meeting their childcare needs, and to help them balance family and work commitments."
The government wants families in every area to have access to wrap-around care at school, although it is not suggesting that every school should have such facilities.
The chief executive of the National Confederation of Parent Teacher Associations (NCPTA), David Butler, said they found the criticism unjust and offensive.
"Working parents are an integral part of modern society and reflect a recognised shift to a situation where both parents work and where many children enjoy the benefits of full time childcare."
Indeed, government policy supported that, he said.
"Parents deserve to be better understood, and not criticised for seeking to place their children in a safe and caring environment."