This type of curriculum is what appears in documents and teachers' plans.
Implicit (or Hidden)
This type of curriculum has to do with how particular assumptions about schooling and learning manifest in practice. For example, when a teacher has her or his desk at the front of the classroom and "teaches" from this area, the message that is being learned by students is that the teacher is in control, including being the knowledge authority, and is the center of attention. The teacher is also of central importance. Another example involves the value of particular topics that is communicated implicitly. Such values can be communicated by time spent, by tone of voice, or by how the topic is treated (e.g., trivialized or marginalized).
The null curriculum is what is not taught. Not teaching some particular idea or sets of ideas may be due to mandates from higher authorities, to a teacher’s lack of knowledge, or to deeply ingrained assumptions and biases. Teachers and schools may not teach that Christopher Columbus slaughtered many of the native peoples he encountered when he "discovered" the Americas. Many teachers are under pressure not to teach evolution.
These three types of curricula can allow us to identify the nature and emphases of the curricula in use in various schools and school districts. The implicit and null curricula are of particular interest for identifying the underlying assumptions and biases of specific curricula and programs.