The forthcoming West End production of The Children's Hour starring Keira Knightley and Elisabeth Moss has extended its booking period at the Comedy Theatre until 30 April 2011, having previously been booking to 2 April.

Knightley and American screen star Moss (best known as the lascivious Peggy Olson in TV’s Mad Men) will star as Karen Wright and Martha Dobie, teachers at a girls’ boarding school who are accused by a disgruntled student of having a lesbian relationship.

The Children's Hour was last produced in London by the National Theatre in 1994. Writer Lillian Hellman’s other plays include The Dark Angel, Watch on the Rhine, The Autumn Garden and her best-known work, The Little Foxes, which was also made into a 1941 film starring Bette Davis.

This revival, which opens on 9 February (previews from 22 January), will be the first new production for former Royal Court artistic director Ian Rickson since his success with Jez Butterworth’s Jerusalem, which transferred to the West End last year after premiering at the Royal Court.

The cast also comprises Lisa Backwell (Evelyn Munn), Isabella Brazier-Jones (Helen Burton), Ellen Burstyn (Mrs Amelia Tilford), Poppy Carter (Janet), Marama Corlett (Lois Fisher), Nancy Crane (Agatha), Amy Dawson (Rosalie Wells), Isabel Ellison (Catherine), Bryony Hannah (Mary Tilford), Carol Kane (Mrs Lily Mortar), Tobias Menzies (Doctor Joseph Cardin), Nathan Nolan (Grocery Boy) and Eve Ponsonby (Peggy Rogers).