It's separating students from A, B, C, D and so on. And the "A students" get the tougher curriculum, the best teachers, etc. Well, they took, over a three-month period, D-level students, gave them A's, told them they were "A's," told them they were bright, and at the end of this three-month period, they were performing at A-level.
Consiste en separar los estudiantes en A, B, C, etc. Y los estudiantes A reciben el plan de estudios más difícil, los mejores profesores, etc. Bueno, ellos tomaron estudiantes de nivel D, y durante un período de tres meses, les dieron las notas más altas, les dijeron que eran estudiantes de nivel A, les dijeron que eran brillantes.