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 (Vars, 1991). 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 (Barton & Smith, 2000).