Interdisciplinary teaching is a method, or set of methods, used to teach across curricular disciplines or "the bringing together of separate disciplines around common themes, issues, or problems.” Often interdisciplinary instruction is associated with or a component of several other instructional approaches. For example, in a review of literature on the subject published in 1994, Kathy Lake identified seven elements common to integrated curriculum models: a combination of subjects; an emphasis on projects; the use of a wide variety of source material, not just textbooks; highlighting relationships among concepts; thematic units; flexible schedules; and flexible student grouping.

There are many different types, or levels, of interdisciplinary teaching. On one end, schools might employ an interdisciplinary team approach, in which teachers of different content areas assigned to one group of students who are encouraged to correlate some of their teaching. The most common method of implementing integrated, interdisciplinary instruction is the thematic unit, in which a common theme is studied in more than one content area.

The example given above about rivers would be considered multidisciplinary or parallel design, which is defined as lessons or units developed across many disciplines with a common organizing topic.

One of the foremost scholars of interdisciplinary teaching techniques is James Beane, who advocates for curriculum integration, which is curriculum that is collaboratively designed around important issues. It has four major components: the integration of experiences, social integration, the integration of knowledge, and integration as a curriculum design. It differs from other types of interdisciplinary teaching in that it begins with a central theme that emerges from questions or social concerns students have, without regard to subject delineations.

In 1989, the seminal work, Interdisciplinary Curriculum: Design and Implementation, edited by Heidi Hayes Jacobs was published by ASCD (Alexandria, Va). In this work, she presented a continuum of options for design spanning focused disciplined work to parallel to multidisciplinary to full integration.

Heidi Hayes Jacobs presents a four-phase approach to curriculum integration planning. First, she suggests that a school conduct action research to learn more about how to implement curriculum integration. This should be done six months to a year ahead of when the school is going to attempt curriculum integration. Next, phase two calls for the development of a proposal. Phase three consists of implementing and monitoring the pilot unit; this should take place in the second year of the curriculum integration plan. Phase four takes place in the third year of the plan, and calls for staff adoption of the program based on the findings from phase three.

Choosing a theme to focus interdisciplinary instruction is a key step in implementing this approach. Themes should be of interest to students and relevant to the required curriculum. In some situations, students might choose the thematic topic. Themes should also be topics of interest to the teacher(s) because successful thematic instructions often requires additional research and preparation. Interdisciplinary themes related to multiple academic disciplines can be reinforced in lessons throughout the school day.

Essential questions are helpful in focusing the theme of interdisciplinary curriculum units. Essential questions are open-ended, intellectually engaging questions that demand higher-order thinking. Essential questions help teachers chose the most important facts and concepts relative to the theme and serve to focus planning efforts. For students, essential questions highlight key facts and concepts related to the interdisciplinary theme. They also serve as a focus for analysis and evaluation. Good essential questions can not be answered with a simple yes/no or true/false; students must discuss, defend, and debate issues related to the theme. Designing interdisciplinary instruction around essential questions require students to learn both content and develop critical analysis skills.