Pop star Olly Murs surprised pupils at his old secondary school when he headed back to the classroom ahead of Children In Need.
The 32-year-old singer returned to Notley High School in Braintree, Essex, to sing his new single, Grow Up.
Murs chatted to his former PE teacher, who is still at the school, and to students.
And he surprised pupils, to promote the fundraising campaign the Big Spotacular, as they gathered at assembly.
The former X Factor presenter said it was "amazing" and "fantastic" to be back, adding: "I've had a lovely day."
He told the Press Association: "A lot has changed since I came here in 1995-2000 ... But there's one old teacher who used to be here when I was - my PE teacher. It was lovely to see him."
Murs, who previously returned to the school with Simon Cowell when he shot to fame as an X Factor contestant in 2009, said he still reminisced about his school days.
"I was an average student. But I used to love school," he said. "It was a great time, I really enjoyed my whole school experience.
"When I was young, my mum and dad always said to me 'Enjoy your school years because you'll always miss them when you get older'.
"I don't miss it every day but I do think of it as a much easier time. You've got less responsibility.
"So it's a good time when you're young to enjoy yourself and have fun and not be too worried about everything. It will all be worth it and work out in the end."
Murs is encouraging schools across the UK to join the Big Spotacular, a fundraising campaign with Lloyds Bank and BBC Children In Need to encourage children and teachers to "go as spotty as possible" by doing everything from dressing in spots to selling spotty cakes to raise money.
He said of the reception he received: "The kids were singing along. They were a fantastic audience."
But he joked that he was disappointed that he could not wear his old school tie.
"They've changed all the ties here. I was going to bring my old school tie but the tie has changed. We had a black tie with white and red and they've got a black tie with white and green. It's a shocker!"
He said of his old school: "Last year they raised £2,000. Hopefully this year they can raise £3,000. If they can do more than that it would be amazing. Children In Need is an amazing charity."
:: BBC Children In Need's appeal night takes place on Friday November 18.