Teachers can use the "Share Classcraft" feature to earn free months toward Premium.
Whenever another teacher signs up for the game through your unique referral link and creates a class, they'll earn two free months of Premium, and you'll earn one free month.
Months earned through the referral system never expire. You can apply them toward a Premium purchase at any time by clicking the "upgrade" button at the top of the screen or by going to My Profile and clicking the green "upgrade your account" button.
You can view how many unused free months you can redeem underneath your referral meter on the right side.
If you successfully refer 10 teachers, you'll receive some free swag courtesy of the Classcraft team!