Set up a "homework options" chart. Maybe put a weekday at the top of each column, allow them to choose from that column. Staple to the top of all completed hw on Friday, with their choice for each night colored in/signed.
I do not believe that giving students a list of words and telling them to memorize it for a test is super effective. I think this spelling activity would encourage students to make relationship to the words, while reinforcing some vocabulary as well.