Here are some ideas for MT program preparation early in high school:
Have your student start learning about the breadth and depth of the Broadway Canon beyond Hamilton and Dear Evan Hansen. A great place to start is to watch the PBS Series, “Broadway: The American Musical” - it is available on DVD.
http://www.pbs.org/wnet/broadway/
The companion book to the PBS series is also an excellent resource - strongly recommended. It really, really helps when you assemble your audition repertoire to know who the major players are: Kander & Ebb, Alder & Ross, Jule Styne, Harnick & Bock, Frank Loesser, not to mention Lerner & Lowe, Cole Porter, Lorenz Hart, R&H, etc.
Watching as many Broadway Golden Age movie musicals as you can is also a very good thing: Cabin in the Sky, Showboat, Oklahoma, Guys and Dolls, Annie Get Your Gun, Damn Yankees, Kiss Me Kate, My Fair Lady, West Side Story, etc., etc. I even made my d watch a couple of Operettas in high school: Desert Song and Naughty Marietta. These shows are great ways to become familiar with the choreography of Bob Fosse, Jerome Robbins, et. al., and that helps with college dance calls.
My d also loved watching the “Broadway’s Lost Treasures” series of DVD’s containing the highlights of old Tony Awards shows. This helps to learn about stars of the past.
Also, staying abreast of contemporary musical theatre is important, the New Musical Theatre web page is a great resource:
http://newmusicaltheatre.com/
Students need songs from both the Golden Age and Contemporary MT for college auditions, and the hunt for the right repertoire be agonizing if you don’t at least some breadth of knowledge in the genre. Hiring a coach to help pick songs can, of course, save a lot of time, but it really helps to be able to have your own ideas and input.
D ended up with more than 100 musicals on her iPhone which she listened to all the time through high school. She has many stories about being able to catch references from her college faculty and summer stock professional directors to Broadway shows while her castmates look blank-faced and whispered, “what is he/she talking about?”
Attending productions, especially professional productions, helps in many ways. Attending a broad spectrum of shows that includes Shakespeare, modern playwrights, cabarets, off-Broadway-type shows, etc. builds awareness of the many facets of the art. University productions are always good to attend.
My d took four years of private piano and music theory in high school which helped a lot in her BFA program. We emphasized with her instructor that the goal was to prepare for music theory placement tests, work on introductory aural training, and develop enough piano skills to pass a basic keyboard barrier in a college BM program for MT majors. We explained that her time for piano practice would be relatively light and she was not interested in doing recitals, etc. (although she did end playing in several recitals anyway). This ended up being a great investment and her teacher was very flexible in working around her high school theatre schedule.