One in five secondary schools is failing to provide adequate ICT lessons for 14 to 16-year-olds, a study by Ofsted has found.
It is a different story in primaries, however, where the subject is used to good effect to increase children's confidence.
Assessment of pupils' work in secondaries is an area of "significant weakness", the school watchdog said. And too much emphasis is put on developing presentation skills at the expense of learning more technical aspects.
Evidence from two years of inspections suggested that standards overall were improving, but too many lessons failed to stretch the brightest pupils.
Inspectors visited 60 primary and 60 secondary schools to assess the quality of ICT. The findings have been published ahead of a longer report into the subject, due to be released later this year.
In primaries, the subject was used well to increase children's confidence and improve their attitudes to learning. "Particular gains were noted for pupils for whom English is an additional language, and pupils with learning difficulties," the study found.
Teachers have made "great strides" in the foundation stage and key stage 1 by using ICT to develop children's independence and creativity. But the momentum was sometimes lost in KS2, inspectors said.
Pupils' achievement was good in about a third of primary schools, but unsatisfactory in one in 10. Primaries are well equipped, but teacher training has not kept pace, meaning that computers and other equipment are not used to their full potential. And more account should be taken of pupils' experience of ICT outside schools.
The findings follow the government-backed Byron review into the potential dangers posed to children from internet and video games. Author Tanya Byron, a psychologist and television child behaviour guru, also called for teacher training to be improved to better protect children and ensure their ICT skills are up to speed.
Lessons in the potential dangers of the internet are neither "coherent, comprehensive, nor consistent", Dr Byron said.