Three schools have been forced to close because of an armed siege at a nearby house.
A suspect in his thirties, believed to have a firearm, barricaded himself in a flat in Leatherhead, Surrey.
Fifty officers, including firearms specialists, surrounded the house and negotiators are trying to persuade the man to come out.
The road was closed off and around 2,000 pupils at Therfield School, West Hill School and All Saints School were asked to stay at home.
A Surrey Police spokesman said: "Officers went to the scene after reports that a man had been seen with a firearm. No shots have been fired and no one has been injured."
There were no reports of anyone else being inside the flat.
The spokesman added: "Access to all three schools is on that road and it was sealed off before the start of school today.
"It would have just been impossible to have had hundreds of children coming through the cordon while there was a incident under way."
Motorists were being advised to avoid the area.