When choosing a play or musical for your school, please take the time to consider the casting requirements of that show. There is an unfortunate tendency among high school and middle school theatre teachers in predominantly white schools to choose plays for which they cannot cast people of color in roles that require it. This means that there have been many school productions of plays like To Kill a Mockingbird, The King and I, Hairspray, and West Side Story where white students have played characters who are intended to be black, Asian, or Hispanic.
Some teachers may think "well sure, it would be better if we had students of color, but since we don't, isn't it okay to substitute for the sake of telling the story?" The answer, from my perspective, is no. Shows like this require the characters to be the ethnicity that they were written to be for a reason. Having a white student play a role like Tom Robinson not only teaches students that whitewashing is okay, but it also undermines the production by neglecting the most important issue of the play.
The argument is often used that if a show has frequently had white actors playing the roles in the past, then high schools should be allowed to continue to do this. Othello is great example of a role that has been played by a white actor in blackface since it was first written, and some teachers may be tempted to use this as an excuse. While I will not attempt to explain in this piece why blackface is unacceptable in theatre or in real life, it is still not acceptable for a white actor to play this role without blackface because Othello's race is such a crucial element of the play.
If your school does have diversity to put on these shows, I encourage you to do so in order to tell non-white stories on the stage, but to do so without actors of color is a misrepresentation of the original intent of the story. If you as the director are a person of color and you believe you have a strong reason that supports the text to have white students in these roles, I, being a white male, do not have the experience or the authority to tell you not to do this, but I advise you to think very carefully about what story you are telling by doing this, and to proceed with caution.
There are hundreds of plays and musicals suitable for schools to produce that do not require whitewashing, so if you do not have students of color, please do yourself, your students, and your production a favor by choosing an appropriate production.