It is assumed the instructional methods are known to result in the intended lessons being learned. We have all seen many teachers act with authority in the front of a classroom (or a clinic or a laboratory or shop or another place where school happens) and tell students what and how to learn the curriculum. There are libraries filed with advice about how best to teach, many are contradictory to each other. Teachers have preferred methods, they have well-reasoned plans, the arrive well-prepared and deliver the instruction just as they planned, and it fails. The reality with instruction is that teachers do not know with certainty how to teach a particular concept to a particular group of students at a particular moment. Teachers must be prepared to critically assess their lessons (even their most-favored lessons) whenever they teach them.