Parrs Wood High School’s Harmony Choir will join the singer on stage during her set at Sunday’s show.
Some of the pupils in the choir were at the singer’s concert last month when 22 people were killed by suicide bomber Salman Abedi.
Teacher Daniel McDwyer, 24, told The Times about his ‘delight’ that the children would be performing.
He said: ‘So so proud! Love you Manchester. Going to be such a beautiful tribute.’
Parrs Wood pupil Shaunna Burns, 17, had won tickets to see Grande at Manchester Arena and took three friends.
She said: ‘It’s so surreal. You do not think one second you are going to see a performer and then the next be on stage with her.’
The choir have also recorded their own cover of Grande’s My Everything as a tribute to the victims.
Tickets for One Love Manchester, which will feature performances from Coldplay, Katy Perry, Justin Bieber, Take That, Niall Horan and Miley Cyrus, went on sale this morning and sold out in six minutes.
Fans complained on social media that technical difficulties prevented them from buying tickets.
Proceeds from the event will go to the We Love Manchester Emergency Fund, which was set up by the Manchester City Council and the British Red Cross to support the families of the victims.
Grande posted an emotional open letter after the attack on May 22 offering her ‘prayers and condolences’ to those affected.
She said: ‘My heart, prayers and condolences are with the victims of the Manchester Attack and their loved ones. There is nothing I or anyone can do to take away the pain you are feeling or to make this better. However, I extend my hand and heart and everything I possibly can give to you and yours, should you want or need my help in any way.
‘We will not quit or operate in fear. We won’t let this divide us. We won’t let hate win… Our response to this violence must be to come closer together, to help each other, to love more, to sing louder and to live more kindly and generously than we did before.
‘Music is meant to heal us, to bring us together, to make us happy. So that is what it will continue to do for us. We will continue to honour the ones we lost, their loved ones, my fans and all affected by this tragedy. They will be on my mind and in my heart everyday and I will think of them with everything I do for the rest of my life.’
Fans who were at her Manchester Arena show were offered free tickets to the benefit gig.
The concert is on Sunday, June 4. Viewers can watch the event on BBC One from 6pm to 9pm, while radio listeners can join in on BBC Radio and Capital Radio.