班主任长得真励志
[bān zhŭ rèn zhăng dé zhēn lì zhì]
'班主任' refers to a class teacher, and '长得真励志' roughly translates as 'truly inspiring in growth.' The nickname might playfully mean this person's headteacher serves as a positive motivation to them in daily life or study. Or it might sarcastically imply the teacher inspires in negative ways by having a stern or tough manner to push students towards self-improvement through challenges.