In classrooms, teachers use a variety of assessments. Formative and summative assessments provide them information on the effectiveness of the instruction they are providing during and after a lesson. Assessments also differ in the type of information they provide. Criterion-referenced assessments measure what students know against a set of skills or knowledge. Results from norm-referenced assessments indicate how well a student did in relation to a group of similar students. Each type of assessment has a function and provides unique information to the system.