The Montessori method cannot be applied to grades beyond elementary school. As a result, students who are accustomed to learning centers may experience a rude awakening when a teacher assigns them required tasks and homework. An intelligent child who has spent much time in a learning center may have difficulty adjusting to the basic structure of the high school lecture.
Criteria for evaluating a child's success in a learning center are not as well-defined as a homework assignment or a test. Left to their own devices, students may focus on irrelevant details or fail to absorb the key principles of a mathematical or linguistic concept. Further, the lack of a letter grade makes it difficult for children and parents to evaluate their progress in school. For this reason, learning centers often conceal students' intellectual progress (or lack thereof).
One method of avoiding the issue of evaluation is to separate students into groups. The regular group is taught a standard curriculum, while a "gifted" group with superior grades or test scores enjoys the privilege of using the learning center. Segregating students may produce feelings of inferiority and alienation in some. Students of the learning center may appear to be "goofing off" to others even when they are enriching their minds.
Learning centers often cost more. In an ideal world, every child would have his own computer to study a subject on a school intranet, but only the wealthiest Montessori schools can afford this. Further, the best learning centers involve small classes in which the teacher can monitor students' progress. When an instructor is present to facilitate a child's activity in a learning center, the number of teachable moments increases dramatically. However, budget cuts make it difficult to employ enough personnel, especially when a single-grade teacher has to divide her attention between a learning center group and a second in a standard classroom.