The quartet will join other former castmates for the Disney Channel get-together, which will air in America on Wednesday (20Jan16).

Zac Efron won't appear alongside his ex-girlfriend Hudgens and their co-stars for the reunion, but he has recorded a message for fans.

High School Musical was Disney Channel's highest-rated programme when it debuted as a TV movie in 2006. It spawned two sequels and the soundtrack became a bestseller.