This lesson plan focusses on educating students about secure passwords:
https://www.wayne.k12.ms.us/userfiles/12/Cyber%20Safety%20Lessons/grade%206%20strong%20passwords.pdf
The NSW Department of Education also have an article discussing how to make a good password:
https://www.digitalcitizenship.nsw.edu.au/articles/what-makes-a-good-password