The thousands of teachers who rallied in central London on Thursday were in fighting mood.

Blowing whistles and chanting slogans, they marched on Westminster waving placards saying "No to pay cuts" and "No extra unpaid hours."

"We're tired of inflation going up and our salaries not meeting that rise," said Leanne Hahn, a primary school teacher from north London.

"We're struggling to get mortgages and to get onto the housing ladder," she told Reuters. "We just can't afford to live."

With some 8,000 schools affected by the strike, criticism of the action from members of the government as parents were forced to find alternative child care arrangements was met with consternation by the demonstrators.

"I'm a parent as well, so I'm on both sides of the fence," said Janet Arthur, another primary school teacher.

"It's alright for them up there, they give themselves nice big pay increases, but what about us? We teach the future leaders, the nurses, the teachers - you can't do without us."

Marchers were also worried about the future of their profession.

"I've been a teacher for a long time, and getting new teachers in is more difficult now and it's also more difficult to keep them," said Steve Charles, head of the English department at Forest Gate School in Newham.

"A lot of teachers come for three years and then find they're not really earning enough, so they leave.

"You're left with this rather strange demographic of very experienced teachers and very inexperienced teachers, but nothing in the middle."

For the National Union of Teachers which organised the march, Thursday's strike was only the beginnning.

"I think the government are being complacent if they think they can impose this settlement of the non-inflation pay rise on teachers without a fight," said Alex Kenny, a national executive member.

"The union has been campaigning and will continue campaigning. Today's strike won't be the end of it."