I think this will differ based on the therapist and school system. I personally like to see my kids one on one. Depending on what we are working on this may be done in the classroom, outside, in the gym, or in the lunchroom. My younger kiddos have a lot of goals for coloring, playing appropriately, self-care skills, or sensory needs. My older students focus more on independent living skills as we begin to prepare them for the transition after high school.
If you have concerns about your child’s needs in the school or if your child has an outside therapy plan that should also be implemented in the school setting I would suggest contacting the teacher and discussing the possibility of OT services in the school. The teacher can direct you in the direction and walk you through the next steps