Educational psychologists have been instrumental in providing techniques that teachers can use to determine how successful students have been in attaining new knowledge and skills. Today, perhaps more than ever, assessing students' knowledge and skills is a central issue in schools. From a teacher's perspective, two of the most relevant purposes of assessment are (a) to identify students who need educational or psychological assistance, and (b) to provide information to teachers that will help them develop instructional programs to facilitate all students' functioning. Assessment involves the use of many tools and a basic knowledge of measurement. These topics are examined in detail in Chapters 12 and 13.