What do polarized student evaluation results say about my teaching?

Evaluations only tell you whether your students liked you or not. Your main goal, however, is to have students learn the material and develop their intellectual skills, not to have them like you.

Have experienced colleagues sit in on your classes and give you feedback, and have colleagues look at your assessments and the students' performance on them (with appropriate attention given to how you prepared the students - at an extreme, assessments mean something different (but not nothing) if you've given the students the questions and answers in advance!). This will give you much more useful information than student evaluations.

From the OP's comments:

Evaluations the students gave the OP:

[...] there are like 3-4 students with really low evaluations.

Grades the OP gave the students:

I had about 20 who received As, around 12 Bs, around 10 in C range, 1 D and an F.

I don't know if I'm misunderstanding, but it sounds like in a class of 44 students, about 8% gave very poor evaluations, while the other 92% gave very high evaluations. I would say that there's some good news and some bad news here.

• If 92% gave very high evaluations, then clearly a lot of things are going right.

• To be unsatisfied with such high evaluations shows, in my opinion, totally unrealistic expectations.

• The grade distribution described here is extremely inflated. It's hard to know what this means without more context. It's possible that this is at a school that has extremely inflated grades in general. (This kind of extreme grade inflation is fairly common in non-STEM courses at expensive private schools that have highly selective admissions.)

Student evaluations are basically measures of two things: (1) whether the instructor did what was expected (showed up for class, knew the subject), and (2) whether the student got the grade they wanted, without an onerous amount of effort. Evaluations are not sensitive measures of the difference between an average teacher and a great teacher.

I would not sweat over it (not yet!). Not because ONLY 58% of students filled the evaluation form and definitely not from teaching your first course! Wait till you teach more courses, gather more data then re-evaluate from there. Teaching requires experience and experience comes with time.

Remember this, how many professors did you have when you were a student that you did not like? Did you not like them because you did not like the course itself? Did not like their personalities? Just because they were mean? Got a bad grade with them? Had you do too many homework, etc. the point is, many students (especially undergraduates) tend to be somehow moody when filling evaluations. I fear sometime that many of these evaluations are based on the professor's charisma, personality, the way s/he dresses, popularity than actual teaching.

One thing you can do is to collect informal evaluations every 4 weeks (or so) of the semester. So, you can see and re-evaluate your teaching methods sooner/faster. This can be done by sending online surveys to the students that let them post their reviews anonymously (You might wanna check your dept.'s rules for this first". Or maybe have short conversations with few students (A-student, B-student and C-student) to get some feed backs. Perhaps you can ask a fellow faculty member to attend your class 1-2 times to critique your teaching methods.