According to the website, "They hope to monetize their product by selling their simple communication system to school administrators".

So this chart shows an increasing number of non-monetizable members... and doesn't show growth in their core product / revenue stream: a paid communication system for school administrators.

This situation is very similar to the whole Groupon subscribers issue - which has proven subscribers aren't necessarily monetizable, or a very small / disproportionate members are...

Thoughts on reporting growth of 'users' vs. growth of 'monetizable users'?

Are any users worth anything, even if they aren't related to the core product?