"I now have two reasons to leave your site. First, you are including more advertisements that are not appropriate for educational settings even with adults and second, and most importantly you are forcing me to open my site to the public so that my students can join. I am sure it takes a lot of code to support the invitation to private sites, but that is part of what a developer does. So let your advertisers know that your lack of initiative has removed me and all of my past and current students from wetpaint."