And because of the increasingly earlier sexual maturity of children, the authors question whether this is appropriate, especially as the schools in question had received a large number of requests from the children themselves for separate facilities, say the authors.
The survey of 116 primary schools in Sheffield, a large city in northern England, included children between the ages of 8 and 12.
Of the 102 that responded, 40 (39%) said that their pupils had specifically asked for separate facilities within the previous year. And around one in five said that parents had also made this request.
But one in five of the schools had no separate changing facilities whatsoever. And although around 8 out of 10 did provide separate facilities for year 6 children (11 to 12 year olds), the proportions steadily diminished for younger children.
Where separate facilities were provided, these tended to be the school toilets for over two thirds of schools, and around four out of 10 schools offered the option of changing in an empty classroom.
Other facilities included the staff room, the school corridor, or other children clustering around to provide a human screen.
The reasons schools gave for their failure to provide separate sex facilities were constraints on available space and/or insufficient staff members to supervise proceedings.
But the authors point out that around three quarters of girls will have some breast development by the time they are 11 to 12. Half will have pubic hair, and around one in 10 will have started their periods.