Solihull's infant classes are the third most crowded in the country. But the schools are extremely popular, and achieve consistently high national test results.
Heads in the borough say their large classes are part of the success, as they can buy in extra support with the cash they receive for additional pupils - which is why both schools and parents are opposed to the Government's scheme.
Parents fear cutting primary classes will force heads to axe ancillary staff, and standards will fall. And they say parental choice will also diminish.
At key stage 1, 49.7 per cent of Solihull children are in classes of more than 31. But all primaries have classroom assistants and many employ part-time specialist staff for special educational needs and music, for example.
Andrew Halstead is a parent-governor at St Alphege Church of England infants school in the affluent south of the borough. He says having six classes of 35 pupils allows the head to employ a full-time ancillary helper in each reception class and a full-time, shared helper in Years 1 and 2. There is also a part-time special educational needs and a part-time music teacher.
"Without substantial Government subsidies, reducing our class sizes would mean getting rid of our ancillaries and the whole ethos of the school would change," Mr Halstead says.
"We can get away with big class sizes here because we have a very middle-class intake and lots of parental support. Teachers are rarely on their own with 35 pupils, even when there is no classroom helper. The Government says it wants to raise standards, but a forced reduction in class sizes would have the opposite effect. Class size isn't the only thing that relates to quality."
His views are shared by Julie Southall, who has has two children at Chapel Fields Junior School, Solihull, where classes are also large. "Like all parents I'm concerned about class size but it's not my main worry," she says. "I'm sure a lot of people voted Labour at the general election because they liked the idea of smaller classes without realising they'd have to pay in another way. Most of us would rather have 35-40 pupils and extra support staff than under 30 pupils and no additional help."
Michelle Watts, whose daughters go to Coleshill Heath primary school in the northern, most deprived area of Solihull, said: "It's very important for parents to be able to choose their children's school. I don't think they suffer from big classes. A good school's a good school, no matter how many children there are."
Solihull's director of education, David Nixon, says he expressed serious doubts about the Government's pledge to DFEE officials last July.
He warned that a forced cut in class sizes would reduce parental preference, and schools' ability to manage their own resources. The powers of statutory appeals panels would also have to be modified.
"I think parents have come to expect being able to express a clear preference of school and although many of them will welcome the Government's promise, I feel that they would rather have the school of their choice with a class of more than 30 than be directed into a school which they don't want with a class of under 30," he says.