Lady Gaga made a surprise appearance at Walter Reed Middle School in Hollywood after a teacher told his class they were about to meet their new substitute teacher. The pupils screamed as Gaga entered in English-teacher-via-Balenciaga garb: a blue trouser suit and heavy-framed glasses. One girl raised her hand in disbelief to ask, “Are you the real Lady Gaga?” before the singer removed her specs to reveal her identity: shock.

Her appearance was part of a collaboration with Staples to raise funds for schools. The office stationery company filmed the encounter to run as a PSA as part of their Staples for Students campaign.

“I want kids to love themselves – fearlessly,” says Gaga in the PSA, having asked the children to draw their dreams and ambitions. “Not having the materials at school is a real problem. That puts a child at a deficit,” she says. Staples for Students have donated $2m to the Born this Way Foundation and DonorsChoose.org, both of which fund class projects and school supplies. Gaga encourages viewers to make their own donations in Staples stores, or through their website, staples.org.

AdWeek says that the encounter was unscripted and the kids’ surprise at seeing the pop-star in their classroom was actually genuine. In light of Lady Gaga’s upcoming Joanne World Tour, Staples for Students have launched a competition, offering one lucky winner with a $50,000 scholarship as well as tickets to see her perform in Las Vegas.

Earlier in the year, the artist made a special visit to the Ali Forney Centre, a place for homeless LGBT youth in New York. She with some of the centre’s young people and performed songs from Joanne.

The first leg of the tour begins on August 1 at Rogers Arena in Vancouver, where we expect she'll ditch the trouser suit.