Christopher Sergel’s stage adaptation of To Kill A Mockingbird debuted in 1991, with school audiences clearly in mind. To compensate for the play’s simplicity, Trinity Rep fusses things up with some odd casting decisions. (Or maybe that’s because they’re simultaneously staging a different play with the same actors?) In one scene, Fred Sullivan Jr. plays both level-headed sheriff Heck Tate and also the villainous Bob Ewell, while an African-American actress plays Mayella, the white woman who falsely claims rape against a black man. Adults play children, and the actors take turns breaking character to tell personal stories about human understanding.