The government-supported National Youth Agency says more time should have been allowed to find the mentors who will work with children on overcoming barriers to learning.
Chief executive Tom Wylie said the schools where pupils are in the greatest need are likely to be the least attractive places to work.
The Government has announced that pound;65m is to be spent up to 2002 on recruiting mentors who could be teachers, education welfare officers, youth and social workers. Pupils to benefit from the scheme could include pregnant teenagers, targeted by the Government's social exclusion unit.
Mr Wylie, a former HMI, said: "I have no doubt that there are people out there who can do it, but the question is whether they will find the people to work in the schools in the most deprived areas.
"These are schools which have enough difficulty in retaining their key staff, let alone attracting mentors. In the inner cities we are talking about schools where the pupils are disruptive and are harder to work with."
"There is a high turnover of pupils," he added. "There are schools in London where the turnover of pupils is almost 100 per cent in one year. That is not an easy environment to work in."
"I would just like to have the confidence that this is seen as a long-term programme and that the building blocks are being put into place."
The NYA is funded by local and national government to promote young people's personal and social development.