Two-fifths of teachers say the Government's new reading test for six-year-olds has helped them identify struggling youngsters.
Ministers said the check would give thousands of children the support they needed to become fluent and confident readers.
Plans for a reading test for six-year-olds were announced by the Department for Education (DfE) at the end of last year, amid concerns that children with poor reading skills were slipping through the net.
The new study, by the Centre for Education and Inclusion Research for the DfE, is based on a pilot of the test, which was taken by Year 1 pupils at 300 schools in England this summer.
Selected findings published by the DfE reveal 43% of pilot schools identified children with reading problems that they were not already aware of. Three in four (74%) teachers thought the check was appropriate, while just under two-thirds (62%) said the experience of taking the test was positive for pupils. A further 31% said it was neither positive nor negative.
Three-quarters of schools also said the test assessed pupils' reading levels accurately.
On average, schools took three hours to prepare for the test and 12-and-a-half hours to administer it.
Schools Minister Nick Gibb said: "The new check is based on a method that is internationally proven to get results and the evidence from the pilot is clear - thousands of six-year-olds, who would otherwise slip through the net, will get the extra reading help they need to become good readers, to flourish at secondary school and to enjoy a lifetime's love of reading."
Official figures published last month revealed that one in 10 11-year-old boys (10%) - almost 28,000 youngsters - reached the level expected of a seven-year-old or lower in reading this year, compared with 5% of girls (just over 13,000 pupils). Overall, 84% of youngsters reached the expected level in reading, up from 83% last year.
Teaching unions have raised concerns about the new reading test, which will be carried out in all English primaries next June, warning it will do nothing to improve literacy in schools.