Some colleges also offer to stage readings and produce plays of theatre majors interested in writing for the theatre. High School Writing plays for high school students is actually one way to make something of a regular income writing plays. Every time a play is produced, the writer gets royalties. Getting plays out into the market here generally means getting a play published and offered through catalogs that offer plays for the school market. This is more of a niche market.
Some theatres specialize in producing theatre for children.
This is a new form of theatre written to be produced and performed on-line. It is so new, how it will evolve will be determined by the theatre artists now exploring the medium. Many people are familiar with the one person performances of well-known figures like Mark Twain and Abraham Lincoln. But there is also a market for one person shows about people well-known in a particular region or for activities that affected particular groups. If you can write such a play and find a performer, these kind of plays can tour colleges, particularly if they are historically accurate.