"It's our turn to affect a positive change, to stand up for equality and to empower others to join us. On 17 April, I will go silent to stand in solidarity with my peers who remain voiceless," she told an audience of thousands of schoolchildren and teachers at the 'WE Day' youth empowerment event in London on Friday.
She wants young people around the world to join her in the day of silence to highlight the need for the world to listen to children's voices.
"We have opportunities to raise our voices. We should use it to the benefit of these children," the Nobel Peace Prize nominee added.
The WE Day event sought to empower children to get involved in making a change through charity work and was attended by students from more than 380 schools across the UK.
Tickets to the show were awarded to children who had done one local and one global charitable action. It included musical performances and motivational speeches by Prince Harry, Sir Richard Branson and Al Gore.