Many educators worry that students are more positive about teachers who give better marks regardless of what the students learn, and are more negative about teachers who make students work hard in order to learn. If this is true, it means the simplest way for a teacher to get a good evaluation is to make it easy for students to get good marks.

As it happens, students who rated their current teacher most highly got better marks in their current course but did much worse in later courses. This confirms the fears of educators: students’ evaluations are linked with current grades, but also with students’ failure to learn things they need for the future. So, a student who is happy with their grade and teacher should worry — they may not have learnt that much. —The Conversation