Miss Slim was amazed to find herself having a chat over the phone with Sir Paul McCartney just moments later. But she was so star-struck at the sudden turn of events that she could barely get any words out.
Miss Slim, a Year 9 teacher at Thomas Adams School in Wem, had been contacted by Sir Paul's management company after her pupils, including Bartek Czaplinsk, wrote to the star asking for donations for a charity raffle.
Her class wrote to a host of celebrities and football clubs hoping to collect prizes for the raffle in aid of children's charity ChildLine.
Miss Slim said: "I called this number back that I didn't recognise and it was his management firm.
"They said he wanted to help and I said 'that's brilliant'. Then they said he'd just walked into the room and would I like to speak to him. You don't say no. I don't think I actually said anything properly. I said 'hello', 'thanks' and ''bye'. I was a bit star-struck."
Sir Paul sent an autographed CD of RAM, an album first recorded with wife Linda in 1971 and re-released earlier this year. Across the cover he has written 'Cheers x Sir Paul McCartney'.
Other celebrities who sent prizes include Sir Michael Caine, the Hairy Bikers, Greg Davies and Jessie J, as well as the casts of Coronation Street and Emmerdale. Liverpool FC sent a pair of boots worn by defender Sebastian Coates.
The raffle has been organised as part of a life skills course the 13 and 14-year-olds are doing, which includes a task to raise money for a good cause.
"The children are really excited. Every day they were asking if the post had arrived. It's good to see people take them seriously," said Miss Slim. The draw for the raffle will be made on November 9. Sealed bids are being invited for Sir Paul's gift and two signed photos from Sir Michael Caine.