How can I be sure my thesis statement will be good enough for my paper?

Have someone read it and give you their first impression of it. I would also recommend giving hints about what is contained in the paper. It kinda depends on what your teacher is looking for though.

My high school teacher said that the thesis should be a summary of the paper. She also said that it should be 9 sentences long, and it should match the closing statement almost exactly. I'm not sure if that is what your teacher is looking for.

You can ask your teacher, or you can simply make it an interesting paragraph or two that grabs the readers attention. Pretend like you are writing for a newspaper... your thesis is your headline. Use it to grab the readers attention and propel them through the paper.

I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.