Our suggestion is that you give parents a date by which you expect them to register for the testing platform. If that date passes and the parent has not registered the child, you can create an account for the student by visiting https://online-test.spellingbee.com and using the student's school email address.
Please note that you MUST visit only the link above to create a student account. Additionally, you should not create an account for your student if his or her parents have expressly stated they do not want their child participating online.