Admission into Teacher Preparation

Preparation programs should screen candidates for academic proficiency.
Evidence is strong that countries whose students consistently outperform U.S. students set a much higher bar for teacher preparation programs than what is typically found in the United States. Research is also clear about the positive effects on student achievement of teachers with stronger academic backgrounds.
Far from the top third or even top tenth to which more selective countries limit candidates, most states do not even aim for the top 50 percent. Many states do not evaluate candidates' academic proficiency as a condition of admission to teacher preparation at all; most others set a low bar.  Some of the states in this latter group require only a basic skills test. These tests generally assess middle school-level skills, and do not ensure that candidates are prepared to do college-level work.  Others have a minimum GPA requirement, but only a handful demand at least a 3.0.
Screening candidates at program entry protects the public's investment.
Teacher preparation programs that do not screen candidates, particularly programs at public institutions that are heavily subsidized by the state, invest considerable taxpayer dollars in the preparation of individuals who may not be able to successfully complete the program and pass the licensing tests required to become a teacher. Candidates needing additional support should complete remediation prior to program entry, avoiding the possibility of an unsuccessful investment of significant public tax dollars.
Tests normed to the general college-bound population would improve selectivity.
In addition to the fact that current basic skills tests generally measure only middle school-level skills, another concern is that they are normed only to the prospective teacher population.  Tests normed to the general college-bound population would shine a clearer light on the academic proficiency of those admitted to teacher preparation programs and allow programs to be truly selective. 
Admission into Teacher Preparation: Supporting Research
For information on basic skills and certification test pass rates across the states, see Secretary's Seventh Annual Report on Teacher Quality 2010.
For evidence that basic skills tests for teachers assess no more than middle school level skills, see "Not Good Enough: A Content Analysis of Teacher Licensing Examinations." Thinking K-16, The Education Trust, (Spring 1999).
For evidence of the predictive power of college selectivity and SAT scores see C, Clotfelter, H. Ladd, and J. Vigdor, "How and Why do Teacher Credentials Matter for Student Achievement?", NBER, Working Paper No. 12828, January 2007 and J. Rockoff, B. Jacob, T. Kane, and D. Staiger, "Can You Recognize an Effective Teacher When You Recruit One?", NBER, Working Paper No. 14485, November 2008. The authors also found college selectivity to have a positive impact on student achievement in North Carolina in "How and Why Do Teacher Credentials Matter for Student Achievement?", NBER, Working Paper No. 12828, January 2007. 
For a discussion of teacher preparation program admissions policies in other countries, see OECD study Teachers Matter: Attracting, Developing and Retaining Effective Teachers, Organisation for Economic Co-operation and Development (2005).  Also see Barber, M. and Mourshed, M., "How the World's Best-Performing School Systems Come out on Top." McKinsey & Company (2007).
For research supporting greater selectivity for teacher preparation programs see, Donald Boyd et al., "The Narrowing Gap in New York City Teacher Qualifications and its Implications for Student Achievement in High-Poverty Schools," National Bureau of Economic Research, Working Paper No. 14021, June 2008; Drew Gitomer, "Teacher Quality in a Changing Policy Landscape: Improvements in the Teacher Pool," Educational Testing Service, 2007; D. Goldhaber et al., NBPTS certification: Who applies and what factors are associated with success?", Urban Institute, 2003; A.J. Wayne and P. Youngs, "Teacher characteristics and student achievement gains: A review." Review of Educational Research, Volume 73, No. 1, Spring 2003, pp. 89-122; Grover Whitehurst, "Scientifically based research on teacher quality: Research on teacher preparation and professional development," Paper presented at the White House Conference on Preparing Tomorrow's Teachers, 2002; J. Kain and K. Singleton, "Equality of Educational Opportunity Revisited" New England Economic Review, May/June 1996, 87-114; R. Ferguson and H. Ladd, "How and Why Money Matters: An Analysis of Alabama Schools," In H. Ladd (ed). Holding Schools Accountable: Performance-based reform in education. Brookings Institution, 1996, pp. 265-298; R. Greenwald et al., "The Effect of School Resources on Student Acheivement", Review of Educational Research, Fall 1996, Volume 66, No. 3, pp. 361-396; R. Ehrenberg and D. Brewer, "Do School and Teacher Characteristics Matter? Evidence from High School and Beyond", Economics of Education Review, March 1994, Volume 13, Issue 1, pp. 1-17; Ron Ferguson, "Paying for public education: New evidence on how and why money matters," Harvard Journal on Legislation, Volume 28, Summer 1991, pp. 465-498; R. Strauss and E. Sawyer, "Some New Evidence on Teacher and Student Competencies", Economics of Education Review, Volume 5, Issue 1, 1986, pp. 41-48; M. McLaughlin and D. Marsh, "Staff development and school change," Teachers College Record, Volume 80, Number 1,1978, pp. 69-94; D. Winkler, "Educational Achievement and School Peer Group Composition," The Journal of Human Resources, Volume 10, No. 2, Spring 1975, pp. 189-204; A. Summers and B. Wolfe, "Do schools make a difference?" The American Economic Review, Volume 67, No. 4, September 1977, pp. 639-652; Eric Hanushek, "Teacher characteristics and gains in student achievement: Estimation using micro data", The American Economic Review, Volume 61, No. 2, May 1971, pp. 280-288.