The man grabbed hold of a child's bag outside Heronsgate School in Lichfield Down, Walnut Tree, at about 08:20 GMT on Wednesday.
The man said, "you're coming with me" before the pupil broke free.
"The incident has been reported to police who are now investigating," the school said. The offender is said to be white and in his 30s.
He had blonde hair and a scratch on his left cheek. He was wearing blue jeans, a blue-green t-shirt and Converse trainers.

The Radio 2 jockey and former Newsnight anchor will be joined by Radio 1 Newsbeat presenter Tina Daheley when the programme returns in September.
They will replace Kirsty Young, Matthew Amroliwala and Martin Bayfield, who have all left the show.
The programme will be shown in a new regular weekly slot, with each episode broadcast live from a "mobile incident studio" near the scene of a crime.
The changes are billed as a revamp for the show, which has been appealing for viewers' information about unsolved crimes since the first episode aired in 1984.
The first four-week series will begin in early September, followed by another block of episodes in early 2017.
Sophie Raworth and Jason Mohammad co-presented episodes earlier this year, but they will now make way for Vine and Daheley.
Crimewatch executive editor Joe Mather said Vine had "the perfect mix of serious journalism alongside genuine empathy towards the victims of crime and their families".
Viewers also know Vine from shows including Points of View, The Politics Show, Panorama and Eggheads, plus as the king of the swingometer in the BBC's election coverage and from his stint on Strictly Come Dancing.
He said: "I grew up watching Crimewatch. It is one of the most powerful programmes the BBC has ever broadcast, with the power to change and save lives, and of course to solve crimes."
Daheley added: "I feel very privileged to join a programme that's allowed ordinary viewers to help bring criminals to justice and make our communities safer.
"Young people often suffer most from crime, so I'm especially keen to use my journalistic skills and experience engaging young audiences at Radio 1 to make sure they feel part of the new-look show."
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A man tried to abduct a boy outside a primary school in Milton Keynes, the school said.
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Broadcaster Jeremy Vine is to be one of the new hosts of BBC One's Crimewatch.