Purchasing your own server will enable you to add multiple teachers without the trial limits. In practise you will be limited by the speed and capacity of the server which limits how many classes can simultaneously use the system. However, an average school (of about 100 teachers) with normal ad-hoc usage should not reach these limits. Normal usage is unlikely to have more than a few classes using the system at any one time, in the same way that physical mini-whiteboards are unlikely to be used by several classes simultaneously. Indeed, a department might share 1 or 2 sets of physical mini-whiteboards.
Before continuing to payment, please confirm your email address via the Google sign-in button below so that we can be sure the purchase will come to yourself. The Google Sign-in you use here will become the administrator account for your server that you will use to add all other teacher accounts.
Note that setting up a server for you takes some human effort (it's not automatic), but we'll be onto it as soon as we can.