You will earn your credential more slowly because you cannot complete as many classes as a full time student. Sometimes classes are difficult to find offered at times you are available to take them. This is especially true of upper division science courses. Whenever possible we offer classes at times conducive to teachers. But the reality is that science classes and their labs tend to be more difficult to arrange in the evenings and summers.
Student teaching is a full time, semester long commitment.
You are expected to be at the school all day long. Most science students are placed in both a middle school and a high school for their student teaching experience. Most will teach one section at middle school and two classes at the high school. That assignment can be rearranged to include two middle school and one high school class. You will ultimately be responsible for creating lessons, teaching classes and grading student work.