Parents at a pair of state-funded faith schools are being asked for voluntary contributions of £1,230 a year.
Parental contributions are not widespread
Governors at King David primary and secondary schools in Manchester say the money helps to keep them high in the "league tables".
They say parents at the inner-city school are happy to contribute.
Some commentators believe this is a growing trend. The government stresses that children whose parents do not pay must be treated equally.
Schools are allowed to ask parents for money but cannot force parents to contribute.
Chairman of the governors at King David, Joshua Rowe, said pupils did not suffer if their parents could not contribute the £1,230 asked for per year.
The school is voluntary-aided and most pupils are Jewish.
Mr Rowe said: "We need to raise a fortune to keep competing with the funding of schools in the independent sector.
"The money pays for extra teachers we need for religious study as well as maintaining buildings and security.
"In Jewish culture, the primary obligation for parents is to educate their children, so parents are quite happy to contribute in this way."
He said there was no question of any child being penalised because their parents could not make the voluntary contributions.
The school is not alone in asking for voluntary contributions although most ask for much less.
The school chosen by Tony Blair for his sons, the Roman Catholic London Oratory School, asks parents to make a voluntary contribution of £50 a year.
John Dunford, the general secretary of the Secondary Heads Association, said he believes more schools are asking for top-up funding from parents.
"It is very difficult to tell, but it is probably growing," he said.
Margaret Morrisey, from the National Confederation of Parent Teacher Associations agreed it was a growing trend.
"This is an enormous amount of money being asked for. It's definitely becoming more common for schools to look for money in this way."
She said schools should consult properly with parents so they could be confident there was no obligation to donate the money and that they could be sure their child would not be penalised if they could not pay.
Some grammar schools also seek extra funding from parents.
Brian Wills-Pope, the chairman of the National Grammar Schools Association does not believe there is a growing trend.
"It's just a few schools, which mainly ask between £10 to £20 a term," he said.
"Two or three years ago, it did seem to be more of a growing trend, when schools were strapped for cash, but schools are receiving more money now - about four or five per cent more this year."
The government does not issue guidance on such fund-raising, leaving the matter up to individual schools.
But a spokeswoman for the Department for Education and Skills said: "However, if they are asking for contributions from parents, they need to emphasise that they are voluntary and that children of parents who cannot contribute must be treated the same."