Teacher hostility and student achievement study

A recent study found that students in a lecture in which the teacher was hostile performed 5 percent lower on average on a test of the content than students in a class with a neutral teacher. Moreover, the students who were naturally oriented to learn to develop their own mastery of the subject, rather than just to get top grades and those who were inclined to put more effort into challenging tasks—in other words, the students mostly likely to be engaged and eager to learn in class—had the scores that were most negatively affected by being exposed to a derisive teacher. The findings also build more evidence of the importance of relationships and respect in student learning. The students in the current study were all undergraduates, so the effects may be different on younger students in K-12. Prior studies have found that students remember put-downs and sarcastic or snide remarks by teachers and consider them a major barrier to learning. 
Goodboy, A., Bolkan, S., & Baker, J.  (2018).  Instructor misbehaviors impede students' cognitive leraning. Communication Education, 67(3), 308-329.
https://doi.org/10.1080/03634523.2018.1465192