At a time when soccer stars are transferred for Pounds 7 million, his school cannot raise the Pounds 3,000 needed for supply cover while he takes up the prestigious post of vice-chairman of the English Schools Football Association.
Malcolm Berry, chief executive of the association, said it was "extremely disappointing to hear that authorities and schools can't get together to support people like John Morton who has been given a national honour.
"This is especially disappointing when teachers like him have given so much of their time to provide extra-curricular sport in areas where there is a desperate need for voluntary activities."
Mr Berry said he knew of many teachers who had to take unpaid leave, or had even moved to different schools so they could carry out duties at national level. "Funding of school sport is a nonsense."
Last week Heritage Secretary Stephen Dorrell announced that he would be publishing a White Paper on the future of sport, including sport in schools, in the early summer. He said it would emphasise the importance of "putting back sport into the heart of school life".
Mr Morton, who holds a full coaching licence, spends hours out of school and in holidays coaching west London youngsters at football, mostly on Tarmac pitches under the Westway dual carriageway.
He said: "I've never had a school playing field, but a lot of kids go on to play at the top level.
"If I was teaching in the private sector there would be no question of getting time off. In the state sector we are desperately trying to keep the sport going - then you get a kick in the teeth like this."
Michael Marland, headteacher of North Westminster Community School, where Mr Morton teaches, said the school was "proud that one of our senior staff will be assisting a national sport's educational activity."
But, he added: "A single school cannot fund a national experience and we are searching desperately for the funding for the good of the country's sports".
A council spokesperson said it was a matter for the school governors as "we have a very high level of budget delegation here".
The general secretary of the Secondary Heads' Association, John Sutton, called Westminster council "parsimonious" for not finding the Pounds 3,000.