Katharine Birbalsingh's public schools in poor areas achieved academic success and were highly praised and consulted by policymakers around the world.

Now the headteacher of Michaela Community School in north-west London is locked in a row with the government over a new issue: the height of boys' trousers.

In a letter to Education Minister Bridget Philipson, Birbal Singh raised objections to proposals in the Government Schools Bill currently before Parliament. But her most high-profile objection was to legislation limiting school uniform symbols.

The bill, which applies to schools in England, aims to limit schools to three pieces of logo clothing or kit, allowing parents to buy cheaper school uniform staples such as shirts or trousers from retailers such as Aldi and Marks & Spencer.

Birbal Singh believes this move is the thin end of a wedge that could eventually lead to sexual exploitation.

"The rule requiring branded trousers may not be obvious to non-teachers, but allow me to explain. In the city center and even further afield, boys who are prone to street problems are the first to pull their trousers down their backs," Bill Balsinger wrote.

"The trousers cannot be removed but are easily identifiable by cleverly positioned signs so that teachers maintain high standards for children, meaning disadvantaged inner-city boys are more likely to feel they belong in their school. It also ensures girls are not left behind Force your skirt to be shortened or your pants to be tightened.

"This limits opportunities for sexual exploitation and ensures that boys and girls are protected from harm. If children in private schools have this protection, then poor children in inner cities should also have this protection."

Michaela's compulsory branded uniform is relatively modest, consisting of just four pieces, including a £32 blazer, sweater and trousers. For older boys, each pair of branded trousers costs £19.50, while Asda sells a pair of trousers for £14.

The government says 24% of primary schools and 70% of secondary schools still require five or more branded items and the measure will save families £50 per child per year. But Birbal Singh said: "The school collects hundreds of second-hand uniforms, dry-cleans them and sells them at a fraction of their original price."

Her letter included a list of other complaints, including the Department of Education's decision to cut funding for public schools that teach Latin.

But before inviting Phillipson to visit Mikayla, Birbal Singh made another personal complaint: "I note that when the House of Commons asked Mikayla to do so, you refused to congratulate Mikayla on her three years of achievement. The highest score in the country for Progress 8 (GCSE results) consistently – something that has never been done before and I don’t know why.”

The Department of Education has been contacted for response.