Rachel Ruzane, 22, saw her four "mentees" at Hackney Free and Parochial school in east London once or twice a week to give them "continuity and routine, and a listening ear." She was taking part in the National Mentoring Pilot Project, started in 1999 by the Department for Education and Skills.
The mentors are full-time university students who are trained and paid pound;6.66 per hour to visit pupils at school and give them one-to-one help to raise their aspirations.
Rachel, who has just graduated from Queen Mary College in east London, was presented with her prize of a laptop and pound;100 in book vouchers by Caroline St John-Brooks, former editor of The TES, at the Guildhall on Wednesday.
She now plans to train as an English teacher.
Second prize went to David Abrehart of Manchester Metropolitan University and third prize to Julie Hames of Portsmouth University. The judges were chaired by David Smith, education officer of the Corporation of London.
More than 900 mentors from 19 universities now provide practical help and encouragement to about 3,500 pupils in secondaries throughout England. But the pilot project only has DfES funding to run for one more year. Charles Clarke, the Education Secretary, said he wants to be convinced mentors make a difference.