Purchasing an upgrade for a subject gives you a choice between 3 and 10 months of access for that subject. If you have a teacher account, that upgraded access does not extend to students who enroll in your classes.
For more information about school licensing and discounted pricing, learn more here: https://www.albert.io/schools/overview
Every subject has free content so you can try it out for yourself before making a purchase decision. Free content is indicated by the open lock symbol.