Justin Bieber, Johnny Depp Pledge Support to Anti-Bullying Film
03/13/2012 AT 04:50 PM EDT
Justin Bieber, Johnny Depp and this year's Oscar winner Meryl Streep are the latest stars to pledge their support to the cause, which was started by Michigan high school student Katy Butler, who has collected almost 300,000 signatures for a petition at Change.org.
Butler, who suffered a broken finger at the hands of bullies, has also won the support of 26 members of Congress.
Streep, 62, will co-host a screening of the film on March 20 in New York City with David Boies, one of the two attorneys responsible for overturning Proposition 8 in California.
– Tim Nudd