Predominantly an American system school and a less an IB program school.
My daughter attended the Shanghai American School Pudong in the IB program between 2013 and 2015. The size of the school is huge, however, the IB section was very small. As a result it offered a limited range of subjects. For instance, our daughter was placed in a Psychology class because there were not enough students for a History class, her subject of choice.
The grading was not purely based on IB methods. Students were graded with the American system and their IB grade was derived from that, which was a disadvantage because the final exams are graded by IB. Academically the school is very strong with excellent records.
Activities outside the curriculum are many and very good.