As is true of many concepts in the field of education, co-teaching has been defined in a number of ways.  Some individuals consider any arrangement with two adults assigned to a classroom to be co-teaching, even when one of the individuals is a paraprofessional or parent volunteer.  A more accurate and useful definition of co-teaching includes these elements:

• Co-teaching is a service delivery mechanism.
  
  Co-teaching exists as a means for providing the specially designed instruction to which students with disabilities are entitled while ensuring access to general curriculum in the least restrictive environment with the provision of supplementary aids and services.
  
  
• Two or more professionals with equivalent licensure and employment status are the participants in co-teaching.
  
  Co-teaching is based on parity.  When paraprofessionals or other adults assist in classrooms, the contribution is valuable, but it is appropriately considered support rather than co-teaching.
  
  
• Co-teachers share instructional responsibility and accountability for a single group of students for whom they both have ownership.
  
  Both educators contribute to instruction as part of co-teaching.  Perhaps the most significant re-conceptualization critical for co-teaching is the notion of a two-teacher classroom--rather than a one-teacher classroom with “help” available from the other teacher.
  
  
• Co-teaching occurs primarily in a shared classroom or workspace.
  
  Although instructional reasons sometimes exist for physically separating students and teachers, co-teaching usually involves multiple activities occurring in one place.  Of course, this implies that co-taught classes tend to be highly interactive places with high levels of student engagement.
  
  
• Co-teachers’ specific level of participation may vary based on their skills and the instructional needs of the student group.
  
  Especially in middle and high school when special educators are co-teaching in subjects in which they have had limited professional preparation, their skill and comfort for contributing to initial instruction may take time to develop.  In such situations, care must be taken to by co-teachers to outline roles and responsibilities so that both professionals do have meaningful roles.