Teachers are encountering increasing numbers of children with stunted vocabularies – haunting many pupils from primary to secondary school – and they fear “vocabulary deficiency” will hold them back educationally and socially.

In response some schools said they had adopted approaches such as highlighting pupils’ use of informal words such as “innit” and encouraging them to improve and widen their use of language.

A survey of 1,300 primary and secondary school teachers across the UK found that more than 60% saw increasing incidents of underdeveloped vocabulary among pupils of all ages, leading to lower self-esteem, negative behaviour and in some cases greater difficulties in making friends.

“This is significant because while language development is a key focus in early years education, relatively little research has been conducted into language deficit as children progress through secondary education,” the report’s authors noted.

Secondary school teachers said that vocabulary deficiency held back pupils’ progress not just in English but also across a range of subjects, including history and geography.

Those with a low vocabulary were also less likely to do well in national tests such as GCSEs, struggling to understand instructions and questions included in papers.