Don't measure your worth by how often you're thanked.
Your job is important. You are important. Your sacrifice is worth it. THANK YOU.
You are noble. Never let the lack of thanks cause you to forget your nobility. Live it. Be it. Be the kind of teacher this world desperately needs.
And for every one of you who are THAT kind of teacher - the world owes you gratitude for which it will never give. But let us teachers give it to one another, for truly, we are among the few who really know what it means to give up your life in pursuit of helping a child find theirs.