Chris Keates said pupils could demonstrate on Saturday

On Tuesday, Live Aid founder Sir Bob Geldof asked: "What's better - two days of work? Two days of geometry?"

But Chris Keates, general secretary of the NASUWT teachers' union urged pupils to make their point online at the Make Poverty History website.

There was "no need for anyone to truant from school" to attend a protest in Edinburgh on 6 July, she added.

'Send a message'

This is timed to coincide with the meeting of G8 leaders at Gleneagles.

Ms Keates said: "NASUWT is actively involved in Make Poverty History.

"This is a crucial campaign and it is vital that the opportunity presented by the G8 summit for a powerful message to be sent to world leaders is not missed.

"However, there is no need for anyone to truant from school to attend. A major rally is planned in Edinburgh for Saturday 2 July and, therefore, anyone who really wants to be involved in a demonstration can."

She added: "NASUWT 's advice is therefore to 'log on' not 'bunk off'."

Sir Bob, former lead singer of the Boomtown Rats, has said he expects one million people to attend the anti-poverty "party" on 6 July.

It comes four days after the five Live 8 concerts, which will take place in London, Paris, Berlin, Rome and Philadelphia.