Brooklyn Publishers publish plays and theater books that are strong, yet void of content issues that would be inappropriate for the markets that they publish for: children's or youth theater, and middle school and high school plays. They accept short play collections, ten-minute skits and plays, ten-minute duets, ten-minute monologues, one-act and full length plays. They look for plays that will appeal to the teen market that address issues in the modern world.
Writer's guidelines can be found at: http://www.brookpub.com/default.aspx?pg=ag&cl=Writers%27+Guidelines
Samuel French, Inc. caters to the junior high and high school markets, but also publishes for community, regional and off-Broadway theater. They are looking for plays that have been successfully produced in established theaters, and require published reviews to be sent in along with submissions.
Submission guidelines can be found at http://plays.about.com/od/playwritingbusiness/p/samuelfrench.htm.
Lazy Bee Scripts specializes in school plays, musicals and pantomimes, but also published plays, one-act dramas, sketches, skits and short plays. They are looking for original scripts and they provide an optional appraisal service. You can find information on their publishing process at http://www.lazybeescripts.co.uk/Publishing/Index.htm.
Eldridge Plays and Musicals publishes works that are suitable for Community Theater, junior high and high schools, as well as plays with religious themes. They cover a wide variety of school and youth play types, including: monologues, collections, plays of social significance, Shakespearean and classic plays, interactive plays and musicals, one-acts and full length plays. You can find writer's guidelines at http://www.histage.com/guideline.htm.
Heuer Publishing is one of the oldest publishers of educational and community theater markets. They are looking for age-appropriate 10- to 120-minute plays in a wide range of genres: drama, comedy, mystery fantasy, farce or melodrama. Themes can be classic, world, ten-minute theatre, social or family. Writer's guidelines can be found at http://www.hitplays.com/default.aspx?pg=ag&cl=Writers%27+Guidelines.