Each year on the first day of school, we send home an assignment for parents called "The Million Word Essay." We ask that they write an essay about their child that describes his/her strengths, weaknesses, interests, fears about the coming year, favorite subjects, etc. Whenever we are concerned about a student, we pull out the folder of letters and see what the parent has to say.
We also spend time at the beginning of the year with the sending teachers (the grade below). They are able to tell us about each student's academic performance, homework tendencies, and so on.
There are several ways a teacher can understand both their learning profile psychology as well as their overall psychological state. The first would be to familiarize themselves with any and all pertinent paperwork. If a student has been documented to have psychological challenges, it would be in the teacher's best interest to read over the paperwork, and develop a plan of action which integrates these realities into how the teacher will interact with the student. Another way of familiarizing themselves with the student's past would be to speak with previous teachers in a professional and proactive manner. This is not idle gossip about a student as much as it is a way to understand with what the student has entered the classroom. I have always found a personal inventory as being quite useful in working with students. It consists of a series of open ended questions that students can answer. Telling them prior to completion that the survey is not going to be used in any way other than getting to know them might help in this process of opening dialogue and doors of understanding.
Getting to know your students is one of the most important jobs a teacher holds. Understanding a student's "psychology" is a very general question. Nonetheless, getting to understand a child period, takes time, committment, and experience. A teacher can do a number of things to accomplish this: reading the child's history from their Cumulative Folders, talking to previous teachers, talking to the child's parents, and even more importantly, speaking with the child. It is imperative that teachers understand a child's learning style and this comes from getting to know them. That is, is the child a kinesthetic, visual, or verbal learner? Being able to speak to what you do in the classroom comes from knowing your students and keeping accurate records and documentation of what you are doing to answer the question "why are you doing that" will also save you in the long run.
When a person is in college to become a teacher, we call this a pre-service teacher, that person is required to take several classes on psychology. The names of these classes are General Psychology, Child Psychology, and Educational Psychology. These classes give the person extensive knowledge in how people think, learn, and grow. The depth of knowledge obtained helps a teacher understand his or her students much better. However, the length of time a teacher has been teaching also helps him or her with applying these techniques.
I hope this answered your question, feel free to post another one if this wasn't what you were looking for.