Yes, of course you may write about Imam Husain (a.s.) and his humanitarian movement in standing against injustice and oppression. I'm sure you are able to be creative in your style and select things to write that would be of benefit to the readers in your school. There are many elements of the personality and revolution of Imam Husain (a.s.), and you will need to take that into consideration when you want to introduce such a wonderful personality to those around you. Write about his sacrifice, his moral life, his social reform movement, the loyalty of his companions, and so on.
With prayers for your success.