Part-Time Teaching Licenses

Part-time licenses can help alleviate severe shortages, especially in STEM subjects. 
Some of the subject areas in which states face the greatest teacher shortages are also areas that require the deepest subject-matter expertise.  Staffing shortages are further exacerbated because schools or districts may not have high enough enrollments to necessitate full-time positions.  Part-time licenses can be a creative mechanism to get content experts to teach a limited number of courses.  Of course, a fully licensed teacher is best, but when that isn't an option, a part-time license allows students to benefit from content experts—individuals who are not interested in a full-time teaching position and are thus unlikely to pursue traditional or alternative certification.  States should limit requirements for part-time licenses to those that verify subject-matter knowledge and address public safety, such as background checks.

Part-Time Teaching Licenses: Supporting Research
The origin of this goal is the effort to find creative solutions to the STEM crisis. While teaching waivers are not typically used this way, teaching waivers could be used to allow competent professionals from outside of education to be hired as part-time instructors to teach courses such as Advanced Placement chemistry or calculus as long as the instructor demonstrates content knowledge on a rigorous test.  See NCTQ, "Tackling the STEM Crisis: Five steps your state can take to improve the quality and quantity of its K-12 math and science teachers", at: http://www.nctq.org/p/docs/nctq_nmsi_stem_initiative.pdf.

For the importance of teachers' general academic ability, see R. Ferguson, "Paying for Public Education: New Evidence on How and Why Money Matters," Harvard Journal on Legislation,Volume 28, Summer 1991, pp. 465-498.

For more on math and science content knowledge, see D. Monk, "Subject Area Preparation of Secondary Mathematics and Science Teachers and Student Achievement," Economics of Education Review, Volume 13, No. 2, June 1994, pp. 125-145; R. Murnane, "Understanding the Sources of Teaching Competence: Choices, Skills, and the Limits of Training," Teachers College Record, Volume 84, No. 3, 1983, pp. 564-569.