It added that teachers felt the "informal style of pupils' personal reading diets" pervaded some pupils' writing - making it too colloquial.
And there were claims that the language of texting and e-mailing was being used when a more formal style was required.
The report looked at how best to boost the performance of children who were falling behind in the core subjects.
The latest results show that four out of 10 14-year-old boys failed to achieve the expected level in last year's national English, maths and science tests.
A third of 14-year-old girls also failed to make the grade.
The Department for Children, Families and Schools report offers voluntary guidance for schools on how best they can help pupils who are at risk of not meeting these standards.
