This is equally true whether the children speak English as a first language or as an additional language, according to academics from University College London and Royal Holloway, University of London.
The researchers compared 782 children speaking English as an additional language with 6,485 monoglot pupils, including those with similar levels of English.
Among those with poor English, academic achievement was similar in Reception, regardless of whether or not English was their first language.
But the research also revealed that many of these children still fell below their class average in Year 2.
'Didn't grow out of it'
Courtenay Norbury, psychology researcher at Royal Holloway and senior author of the paper, said that she had anticipated that those children who spoke English as an additional language would be doing well by Year 2.
“But, actually, their poor outcomes persisted,” she said. “They didn’t grow out of it with more time in the English school system.”
Bilingualism is widely considered to be an advantage for children academically, the academics said. However, their study – which is published in the journal Child Development – found that the cognitive advantages of bilingualism helped with academic achievement only if children’s English was good enough at the start of school to ensure that they were fully engaged with their lessons.
Professor Norbury therefore said that it is imperative that teachers identify early on which children have poor English proficiency, and offer them extra support.
“Oral language proficiency is a key predictor of early school success for all children, whether they are monolingual or bilingual,” she said.
The researchers concluded that the best solution would be to measure pupils’ skills in their first language, in order to gauge whether their problems stem from lack of exposure to English, or from an underlying difficulty with language. But, with the diversity of languages spoken by English schoolchildren, they said, this is impractical.
“But we found that measuring their skills in English, while not perfect, is a helpful predictor of future success,” said Katie Whiteside, of the psychology department at Royal Holloway, and the study’s lead author.
Want to keep up with the latest education news and opinion? Follow TES on Twitter and like TES on Facebook