A member of staff called the police at 9.05am after the girl spoke about the incident in Wagbullock Rise, Easthampstead.
The man attempted to grab the girl at 8.20am but she managed to run to a friend's house.
He chased after hew but she managed to escape out of sight.
The man is described as white, aged approximately 40-years old, and was wearing a grey hooded top with the hood up and grey tracksuit bottoms.
Insp Jon Goosey, Deputy Local Policing Area (LPA) Commander, said: "At this time we believe this is an isolated incident but I am very concerned about the man's behaviour.
"I would like to reassure the community that we will take any reports of this nature extremely seriously.
"These types of incidents are rare but we will investigate any reports immediately."
If you can help, call Det Sgt Peter Wall at Thames Valley Police via the 24-hour Police Enquiry Centre on 101. If you don't want to speak to police or leave your name, call the charity Crimestoppers on 0800 555 111.