If the title is "After Hours in Kindergarten" then the theme is about what goes on in a kindergarten's experience while in school. It provides the theme and tells you what you’ll be reading about.
If your school is using the Scripps National Spelling Bee program, (which most schools in America do), try going on their website. All the practice words are on there. Go to spellingbee.com. Also, you can take those words and put them on Quizlet and make your own flashcards. Hope this helped!
pre-history
Pre is the prefix history is the base word/root word.
Hope I was able to help. :)