The school issued the urgent message this morning, Wednesday, saying there was a "structural issue".
They said the High Street side of the school is "currently unsafe" and the school has been forced to temporarily close.
And they have asked parents to collect their children from the Dallas Road entrance as soon as possible.
The school statement said: "*Urgent* - Due to a structural issue we are having to send all our children home.
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"Please come to collect your child from the Dallas Road entrance of school.
"Your child cannot leave unaccompanied, a known adult must collect them. Do not approach from the High Street side - this is currently unsafe.
"Thank you for your co-operation."
It is believed building work being carried out nearby may have led to some insecure masonry in the area, and Dallas Road made the decision to close the school as a precaution.
Lancashire County Council have been approached for comment.