Only users with a "Provider" account type (users with a provider account are able to create/edit/ and delete student charts). Those with professional titles such as "teacher", "counselor", etc. that have a "provider" account will be charged.
When you sign up as a provider, you are asked to enter a "Billing Email" which is the person who will be responsible for handling payment. This person must be a registered Provider and can be the same person for groups of Providers at a school or within a school district.
Parent and teacher account types are always free.