More than 20 Sir John Gleed School students and two members of staff spent a day helping shoppers pack their bags.
The youngsters lent a hand at Morrisons in Pinchbeck to raise funds for the Rock Challenge Team.
The team raised more than £1,200 for costumes, set, scenery, hair and make-up for their competition performance “Time is Precious”.
They will compete in Grantham next month and Grimsby in July.
A spokesman for the school said: “We would like to thank the staff and customers for their support with this challenge.
“Our students gained a well-rounded experience of communicating and dealing with the public, a life skill which will help them in the future.”