In order to teach students effectively, teachers need to understand the developmental stages that children go through, as well as the difficulties that individual students may have in hitting developmental milestones. Children develop cognitively, linguistically, physically, psychosocially and emotionally from birth to adulthood, and understanding which stage each child is at can enable a teacher to reach that child most successfully. Educational psychology teaches what each of these stages entail, as well as how to deal with the challenges that occur at each stage.
Although adults take learning skills for granted, acquiring new information entails various strategies and procedures. Understanding how children learn information -- both content-based and skill-based -- enables teachers to better orchestrate the learning process in their students. Teaching students involves more skill than simply feeding them facts; students must also learn problem solving skills and thinking skills, as well as the ability to learn independently.
Educational psychology describes the instructional strategies that teachers can use in the classroom. Managing a classroom full of students with various learning styles can be a challenge for a new teacher, but learning how to motivate students, differentiate instruction for students on different levels and discipline effectively can reduce teacher frustration and improve student performance. Research-based strategies often produce better results than simply stepping into a classroom and attempting to teach. Educational psychology instructs teachers in these strategies.
Although "giving tests" has been a common method of assessment for over a century, accurate assessments can be tricky to create. Understanding the goal of assessments -- to identify students that need additional support, and to give teachers feedback on which instructional strategies are working effectively -- is often the first goal of teaching assessment. Educational psychology also examines which types of assessments accurately reflect what students have learned. Teachers who can assess their students skills and knowledge well will have a step up on being able to teach effectively.