Other activities such as driving lessons, dances and scouting are also being cut or changed by school principals worried about legal action being taken against them in the event of accidents, injuries or other mishaps.

The findings have been published by the American Tort Reform Association, which sent questionnaires to randomly-selected members of two national principals' associations.

A total of 65% of the 523 principals who replied reported changes in school activities because of liability concerns.

And a quarter of them said their schools had been involved in lawsuits or out-of-court settlements in the past two years.

Hugging banned

Some schools reported banning all physical contact, including hugging, because they were worried staff could get accused of improper behaviour.

Vincent L Ferrandino, Executive Director of the National Association of Elementary School Principals, said: "Principals honestly lament the freedom they've lost simply to hug a child any more."

The survey found that 20% of the principals who responded reported spending five to 10 hours a week in meetings, or documenting events in efforts to avoid litigation.

Two thirds said more legislative reform was needed. Many said there was a need for more protection for teachers, staff and administrators, a clarification of special education laws, protection from frivolous lawsuits, and limits on punitive damages.

Mr Ferrandino said: "Whenever we plan for anything in a school today, our first consideration is how to avoid a lawsuit.