Question: Who starred in a 1956 American psychological horror-thriller film directed by Mervyn LeRoy and was first became known for her role as schoolteacher Rosemary Sydney?

Context articles: Secret Window
Fools for Scandal
Eileen Heckart
Would You Rather (film)
Hide and Seek (2005 film)
After.Life
The Killing of a Sacred Deer
The Bad Seed (1956 film)
Split (2016 American film)
Waterloo Bridge (1940 film)

Secret Window is a 2004 American psychological horror-thriller film starring Johnny Depp and John Turturro.
 It was written and directed by David Koepp, based on the novella "Secret Window, Secret Garden" by Stephen King, featuring a musical score by Philip Glass and Geoff Zanelli.
 The story appeared in King's collection "Four Past Midnight".
 The film was released on March 12, 2004, by Columbia Pictures; it was a moderate box office success and received mixed reviews from critics.
Fools for Scandal is a 1938 screwball comedy film starring Carole Lombard and Fernand Gravet, and featuring Ralph Bellamy, Allen Jenkins, Isabel Jeans, Marie Wilson and Marcia Ralston.
 It was produced and directed by Mervyn LeRoy and was written by Herbert Fields and Joseph Fields with additional dialogue by Irving Brecher and uncredited contributions by others, based on the unproduced 1936 play "Return Engagement" by Nancy Hamilton, James Shute, and Rosemary Casey.
 The songs are by Richard Rodgers and Lorenz Hart.
Eileen Heckart (March 29, 1919 – December 31, 2001) was an American actress of film, stage, and television.
 Primarily known as a character actress, her career spanned nearly 60 years.
 She first became known for her role as schoolteacher Rosemary Sydney in the original 1953 cast of William Inge's play "Picnic" on Broadway.
 She won an Academy Award for Best Supporting Actress for her performance as the overprotective mother of a blind adult son in "Butterflies Are Free" (1972), a role she originated on Broadway before playing it in the film.
Would You Rather is a 2012 American psychological horror-thriller film starring Brittany Snow and Jeffrey Combs.
 It is based on the party game "would you rather," and centers on Snow's character, Iris, as she attends a dinner party, where she must partake in a life-threatening game to help her sick brother secure a donor.
 The film premiered at Screamfest 2012.
Hide and Seek is a 2005 American psychological horror-thriller film starring Robert De Niro and Dakota Fanning.
 It was directed by John Polson.
 The film opened in the United States on January 28, 2005, and grossed $122 million worldwide.
 Rotten Tomatoes cited praise for De Niro and Fanning for their performances, though its consensus called the film "derivative, illogical and somewhat silly".
 Fanning received an MTV Movie Award for Best Frightened Performance in 2005.
After.Life is a 2009 American psychological horror-thriller film starring Liam Neeson, Christina Ricci and Justin Long, directed by Agnieszka Wójtowicz-Vosloo from her original screenplay.
The Killing of a Sacred Deer is a 2017 psychological horror-thriller film directed by Yorgos Lanthimos, from a screenplay by Lanthimos and Efthymis Filippou.
 It stars Colin Farrell and Nicole Kidman.
 It was selected to compete for the Palme d'Or in the main competition section at the 2017 Cannes Film Festival.
 At Cannes, Lanthimos and Filippou won the Best Screenplay award.
 The film is scheduled to be released in the United States on October 20, 2017, by A24, before being released in the United Kingdom on November 17, 2017, by Curzon Artificial Eye.
The Bad Seed is a 1956 American psychological horror-thriller film with elements of melodrama and film noir, directed by Mervyn LeRoy and starring Nancy Kelly, Patty McCormack, Henry Jones, and Eileen Heckart.
Split is a 2016 American psychological horror-thriller film written and directed by M. Night Shyamalan.
 The film stars James McAvoy, Anya Taylor-Joy, and Betty Buckley, and follows a man with 23 different personalities who kidnaps and imprisons three teenage girls in an isolated underground facility.
Waterloo Bridge is a 1940 remake of the 1931 American drama film also called "Waterloo Bridge", adapted from the 1930 play "Waterloo Bridge".
 In an extended flashback narration, it recounts the story of a dancer and an army captain who meet by chance on Waterloo Bridge.
 The film was made by Metro-Goldwyn-Mayer, directed by Mervyn LeRoy and produced by Sidney Franklin and Mervyn LeRoy.
 The screenplay is by S. N. Behrman, Hans Rameau and George Froeschel, based on the Broadway drama by Robert E. Sherwood.
 The music is by Herbert Stothart and cinematography by Joseph Ruttenberg.