Effective teachers use a variety of methods to determine if a lesson has been successful, so your response should acknowledge this. Plan on briefly referring to some of the assessment tools you use, such as exit tickets or discussions, then tying in the fact that one of the best ways to tell when a lesson is successful is when students are excited about the topic and engaged in the lesson or activity. You want the interviewer to know that you understand the importance of assessments, but that you are also able to gauge students’ understanding during a lesson and can adjust your teaching accordingly.