BHA researchers carried out a simple web search to identify potential breaches of the rules and then looked in depth at the first 100 schools that came up.
They said these were dominated by faith schools, many of which are required to pay a share of building maintenance costs.
Reminder letters
One Church of England primary, highlighted by the BHA, asks parents for an annual payment to what it calls its "Building Fund/Capitation for parents".
"This is not a voluntary contribution but it is a payment all Church of England schools require to maintain the school buildings and classrooms," it says.
Another school - a Catholic primary - says: "We will be asking all who have not contributed to the Building Fund yet for their contribution and writing to them at the beginning of next half term."
A third school explains that "as a voluntary aided school, parents of the pupils... are responsible for contributing 10% towards all building works", before going on to ask for £100 per family.
'Incredibly worrying'
A number of schools also stressed that the requested contribution, far from being voluntary, was a minimum amount, encouraging families that could afford to pay more to do so.
Another school suggests parents should contribute to the fund by using the money they were saving as a result of receiving free school meals.