According to the U.S. Agency for International Development, there is "an inverse relationship between class size and learning outcomes;" the larger the class, the lower the learning outcome. This can be attributed, in part, to the fact that larger class sizes do not give teachers the opportunity for individualized teaching. Every student has her own methods of learning and should receive individualized attention from the teacher in order to learn effectively. Individualized instruction keeps the curriculum the same for every student but individualizes the means of instruction for optimum learning outcomes. This, however, is difficult with large classrooms.
On top of being unable to understand the learning needs of each student, teachers in large classrooms may have difficulties getting to know their students as individuals. Smaller classrooms often require less discipline from the teacher and can result in more time for teaching. Larger classrooms in which individualization is not possible can suffer from classroom management issues.
Because of the time it takes to instruct a large group of students, teachers working in a large classroom often do not have enough time to cover as many subjects as teachers working in a small classroom. A 2007 report by the U.S. Agency for International Development includes findings that teachers teaching in a large classroom "devote less time to math instruction and integrated reading and writing tasks" and, on top of this, do not have time to address art, history, social studies and other humanities subjects.
The size of a classroom can affect the social and academic engagement of the students involved. As reported by the U.S. Agency for International Development, smaller-sized classrooms can create a feeling of community for the students. The research suggests, however, that students in larger classes often do not have this sense of community, and are less engaged in both the social and academic aspects of school because of it. According to studies, this lack of community can also create a negative atmosphere for the teacher, impacting "teachers' morale and enjoyment of their profession."