The author then describes common misperceptions and misunderstandings about Bloom's learning of mastery. Some educators believe that implementing Mastery Learning takes too long and can replace valuable instructional time. In response to the argument, the author admits that the process can be lengthy at first and that many teachers who are implementing the program in their classrooms find that they are behind in units compared to other teachers who are not participating in mastery learning , but teachers can make up for lost instructional time by eliminating lesson reviews before administering formative assessments or by adjusting curriculum and/or pacing