Subjectivity can be something other than racial bias or political leanings reflected in one's teaching. The teacher who is able to select his or her own materials, for example, texts, handouts, and videos, may be subjective racially or politically, or in a myriad of other ways. I, for example, have a tendency to dismiss much of pop culture as I teach. This is purely subjective on my part, since there is value in pop culture, too. Some teachers will have a subjective proclivity based on gender, since often, what we value in classroom behavior is more likely to be produced by females than males, at least in the early years of education.There are countless other examples of subjectivity in teaching.
On the other hand, as Parker Palmer famously said, "We teach who we are." Our value is in our not being robots, but human beings, who bring to the classroom the sum total of our experiences and genes. Generally, students are exposed to a variety of subjectivities in their teachers, enough to help them understand that everyone is different and that as they go out into the world, they will need to learn to function in a world of subjectivity.