Two hot up-and-coming starlets have been announced to star alongside Zac Efron and Vanessa Hudgens in the next instalment of High School Musical.

Mark Propkop and Jemma McKenzie Brown will be joining the rest of the gang at East School High reports OK! magazine.

Although little is known about their roles in High School Musical 3, the twosome have beaten scores of children who auditioned for roles in Kenny Ortega’s series of family fun movies.

One source says of British-born Jemma: "She’s 13 years old and beat out 600 girls from three countries."

As for Matt, his face may seem familiar from guest spots on shows such as Hannah Montana and The Office.

High School Musical 3 starts production in April and is scheduled for release on 24th October.