The school in Southport Road said it was notified of the positive test result just a couple of hours before classes were due to begin on Monday morning (October 12).
Staff rushed out emails to parents just before 8am, informing them of the infection and urging them not to send Year 8 children to school.
The school said an investigation would take place immediately to identify those children who might have been exposed to the contagion, with efforts to track those pupils expected to take all day.
Parklands apologised to parents for the short notice, but warned that any Year 8 pupils who attended school that morning would be sent home.
The message said: "Please note we have just been notified of a positive case in the Year 8 bubbles.
"Please do not send any year eight children to school this morning. We will need to investigate any children who may have come in close contact with a positive case. This will take us most of the day.
"Any child who arrives at school you will be contacted to arrange either collection or your child will be sent back home.
"Apologies for the short notice but we have only just been notified of the positive case and in order to safeguard all pupils and staff we need to take this action."
You can find a complete list of Lancashire schools that have been affected by COVID-19 here.