The national literacy hour could make it harder for schools to "fit in" volunteers prepared to work with struggling readers.
According to VRH, timetable demands are forcing schools to reconsider how they organise other literacy support work.
Melissa Drayson, VRH's southern co-ordinator, said feedback from its survey (see above) had raised the issue. She is confident schools will continue to make time available for one-to-one work.
But she noted: "With timetables being squeezed, schools are saying that it's going to be more difficult to fit in volunteers, because it doesn't fit in with the literacy hour."
Another concern is the withdrawal of struggling pupils from classes, an aspect of other literacy support programmes.
Angela Hosbaum, of the Reading Recovery National Network at the University of London's Institute of Education, said: "These kind of withdrawal activities are going to be problematic. But I don't think it is that much harder than it always was to make these tricky decisions."