Grumba

Normally used to name nice math teachers (which aren't a lot). Grumba teachers are nice at exams, likes to do some games during class and are the best teaching.

Teacher: Hello guys I love to play games with you all in the classes!
Student: Oh that is such a Grumba

Teacher: Hello class. Good news everyone aced the test!
Students: Omg Grumba you are the best!

Teacher: Hey, you understood everything?
Student: Yeah because you teach as a Grumba