Null Curriculum (also known as Excluded Curriculum)
The Null Curriculum is that which is not taught. Sometimes the teacher ignores some content or skill, deliberately or unknowingly. A teacher may consider some idea unimportant and ignore it. Similarly, teacher may avoid detailed description of some topic for the one or other reason, for example, evolution in Biology. Sometimes also, the learner fails to learn certain knowledge, skills or attitude for various reasons.