New Government figures have revealed that a quarter of 11-year-olds are failing to attain expected levels in spelling, punctuation and grammar.
The finding is based on the results of key 2 stage reading, writing and maths assessments taken by more than half a million 11-year-olds in May this year.
In spelling, punctuation and grammar, a quarter - or 139,000 pupils - failed to reach level 4 (good), with boys performing worse than girls.
Almost a third of boys did not reach the expected level - almost 85,000 pupils - compared to a fifth of girls -
almost 55,000 pupils.
Overall, more than 408,000 reached expected levels in the 3 Rs of reading, writing and maths - a one percentage point increase from last year.
Education Minister Elizabeth Truss said: "Today's figures show the majority of children are performing well and they, along with their parents and teachers, should be congratulated for their achievements.
"However, the statistics also reveal that one in four children is leaving primary school without a firm grasp of spelling, punctuation and grammar. The new test encourages schools to focus on these basics.
"British businesses are very clear - written communication has never been more important. Children need to be able to spell well and write proper sentences to get on in life."