In "To Kill a Mockingbird" what is a thesis for don't judge a book by its cover, stand up for what you believe in, and respect your elders?

All of these sub-points could fall under a thesis statement that has to do with lessons that one can learn from the book "To Kill a Mockingbird."  Another thesis statement that they could all fall under is valuable lessons that Scout learns throughout the course of the novel.  You could also use those subpoints to argue the main thesis point of lessons that Atticus tries to teach his children, either through example or action.

Once you pick a main thesis idea, it helps to formulate a sentence that captures that idea.  So, for example, "In 'To Kill a Mockingbird', Atticus teaches his children valuable lessons."  Or, "In 'To Kill a Mockingbird,' Scout learns several very important things that will help her in her life."  Or, "In 'To Kill a Mockingbird,' Harper Lee uses the characters and situations to promote several important morals."  Then, using that main sentence as a guide, use those three individual sub-points, with examples for each. So, for the first point of not judging a book by its cover, you could use Tom Robinson or Boo Radley, and discuss how they don't end up being what they seem.  Other characters to fall under this category are Mrs. Dubose, and Atticus himself (as he shoots down the rabid Tim Johnson).  For the second point, you could use Atticus as he defends Tom's innocence at the possible threat of danger to his children, and Mrs. Dubose as she goes off her pain addiction to be clean before she dies.  For the last point, you could use how Atticus teaches Jem to respect Mrs. Dubose, an elderly woman, or how he always supports Cal's opinion on issues. Discuss each of these examples for each sub-category, all under the main umbrella of the one thesis statement that you end up choosing.

I hope that those ideas helped a bit; good luck!