in thai believe a great teacher is one who creates a classroom environment that makes their students 1.) 'curious', 2.) want to 'explore' ('investigate') and 3.) allows them to 'discover'. I think instilling and encouraging these three elements in students makes a great teacher.
Is 'curiosity' valued in your classroom? A great teacher creates a classroom environment that makes the students 'wonder' about the things they're teaching? You can tell if they are asking questions. Or are they just 'consuming' information?
Do the students want to explore and investigate the topics being taught? A great teacher creates an atmosphere and motivates their students to want to explore and investigate, for example, through experimentation.