The Qualifications and Curriculum Authority said it wanted to ensure children were able to communicate "clearly" in all settings.

The move comes amid concern that excessive television and computer use are damaging conversational ability.

The QCA's 60-page booklet - Introducing the Grammar of Talk - will be available to schools in England from October.

'Appropriate words'

Children aged 12 to 16 will learn the benefits of using correct grammatical constructions, such as "you were" rather than "you was", in everyday speech.

They will look at how they use speech differently when talking to friends and when addressing a large group in a formal setting.

It is hoped this will improve their social skills and career prospects.

A QCA spokesman said: "This is based on recent research in universities. For the first time, teachers will get structured guidance in how to help pupils with speech.

"Children will learn what is appropriate in a certain context."

As part of the national curriculum in English, pupils are expected to develop writing, reading, listening and speaking skills.

The QCA is hoping that discussing the "grammar of talk" will help the latter two.

Part of the guidance relates to the "shape and structure of talk", telling children how and when to use words like "right", "OK" and "really".

The booklet also focuses on the skills of face-to-face communication and unplanned conversations, with emphasis on informal phrases such as "like you were saying" and "to go back to".

The QCA spokesman said: "Over the last five years we've focused on literacy, but there is a whole spoken language out there which operates very differently."

The guidance book will not look at regional dialects.