A group of travellers have set up camp on the field behind Tytherington High School.
Around 15 caravans began using the field between the school and the Middlewood Way yesterday.
It is believed they are on their way to the Appleby Horse Fair in Cumbria.
A spokesperson for Tytherington High School confirmed the matter has been reported to the police.
A neighbour, who asked not to be named, has also reported the matter to the council.
He said: "I went for a jog in the morning and saw one or two camped up, and then I went again in the evening and there were 15 -20 there. I felt quite threatened.
"They have smashed down a fence to get all the caravans on there and kids going to Tytherington are now having to walk through a gypsy camp to get to school."
