Assessments determine knowledge, attitudes, skills, and/or beliefs. There are diagnostic assessments to be administered at the beginning to determine pre-existing skills or knowledge, then there are formative assessments which can help me determine ongoing learning, and lastly, summative assessments to account for learning at the end of the instruction.
I rely on the use of assessments to determine student learning and improve on my teaching. I have never taught a class the exact same way because each class has students with different learning styles and adaptation levels. Don't be afraid to adapt to your students.
