Researchers from York University warned that secondary teachers could be failing to notice reading difficulties suffered by their students.
The study of 857 pupils across 28 state schools also found that 53 per cent of pupils who had serious reading problems were registered as having special educational needs (SEN).
But in once case, a 15-year-old pupil was not on the SEN register despite having the same reading ability as a normal eight year old.
The findings could be an underestimate because some pupils may be on the SEN register for other reasons than reading problems, the researchers added.
Dr Sue Stothard, who co-authored the study, told the Times Educational Supplement: "It is a very important question for teachers and the Senco (special needs co-ordinator) on how the SEN register is managed. Is it identifying all children with difficulties and making sure they get appropriate support."