In practice a lesson on Wiztut whiteboard will be more productive with no more than five attendees, but we do not enforce any limitations. See other FAQ. Hence there is no limitations to how many students can attend one online lesson. Of course the tutor who is conducting the lesson must have enough bandwidth to accommodate the number of students he or she wants to allow in his or her class.
Though the more students are in one classroom the more server processing power and server time will be used which will mean higher server cost, but Wiztut policy is to allow reasonable size group lessons for all of our tutors. It is a good teaching and pedagogic practice to keep your the number of students attending an online lesson to five or less.