Many times teachers think the test items developed by publishers are superior to their own test questions. Publisher tests are constructed by teachers just like yourself. Publisher tests may help a teacher, but they are not superior to the teacher's efforts. It has been said by some that publisher tests are standardized and thus are superior to teacher-made test items. This principle needs to be dealt with from the administrative viewpoint as well.
Some administrators require their teachers to use the tests designed by the textbook publisher.
This may appear to standardize teaching and testing, but it does not. The truth is you have one person, your teacher, teaching the course and another person, the publisher, evaluating what your teacher is teaching. In such a situation you are teaching by one set of criteria and testing by a separate set of criteria. They may intersect many times, but they do not match. The textbook is a tool for the teacher who knows the goals and objectives for the class and understands the academic needs of the students.