The number of volunteers in reception classes has almost halved in the past five years, according to a survey.
The reasons behind the dramatic drop - from 23,600 to 12,900 - are not clear, but teachers and heads suggest they include a rise in the number of parents working full-time and a reluctance to go through Criminal Records Bureau (CRB) checks.
In nursery schools and primaries with nursery classes, the drop in the number of volunteers was more than matched by an increase in paid staff - overall staff numbers stayed roughly stable, at about 6,000 early-years staff working in nursery schools, and 63,000 in nursery and reception classes in primaries.
But while there was also an increase in paid staff in primaries without nurseries, the huge drop in volunteers meant overall numbers went down by 17 per cent, roughly matching the 14 per cent drop in the number of places.
David Fann, head of Sherwood Primary in Preston, said he believed there were a number of reasons for the sharp decline in volunteers.
"CRB is an issue, although it is done without cost to the parent," he said. "In our school, the number of parents who are able to come in has certainly reduced because they are working or have other commitments.
"But this year we are running a course with the local authority aimed at parents who want to come into school to help. It covers child development and what we do in school, and 16 parents have signed up. It may be just this cohort are particularly supportive, I don't know."
On the TES online staffroom forums, teachers failed to agree about where the volunteer parents had gone.
One user, Comenius, said: "Some of the parents where I teach said they would love to come in and help, but refuse to have the CRB check."
Thumperrabbit added: "One mum once told me that she was told that they had a lot of problems with other parents complaining that their child was reading with a mum, not a teacher."
The survey also found that the number of primary schools without nursery classes had dropped from 9,200 to 8,700, whereas the number of primary schools offering nursery provision had risen from 6,300 to 6,700.
The research was based on a survey of 539 primaries with nurseries, 603 primaries without nurseries and 179 nursery schools.
A mother's-eye view
I'm a volunteer for the reception class at my daughter's school, where the kids `read' to me once a week. I was also on the committee of the pre- school, where it was a hell of a hassle trying to find parents to help out.
We had a rota where each non-working parent (who didn't have babies) would help out each session, preparing snacks and helping tidy and wash up afterwards. It was always the same people that would help out - the rest would drop the kids and run.
Ditto the end-of-term deep-clean, where we'd ask parents to help give the premises a good once-over. Most never came and the burden fell to the usual faces. And as for filling committee positions, we almost closed several times from lack of interest.
I think many parents don't understand the concept of community pre-schools and treat them like private nurseries. A great shame.