Here’s another option for a collaborative whiteboard. The free plan offers 10 saved boards and enough features to be useful. The paid plain is 5 Euros a month, and adds other features such as screen recording and 1,000 saved boards.
Sign up is quick an easy, you can use either a Google log in or a Facebook login. One word of warning. Since the company is based in Croatia, they don’t recognize FERPA or COPPA. This may make using the site touchy with students, depending on how your district handles student information.