Boosting early retirement in cash-strapped districts does not hurt students' math and reading scores, according to new studies released at the American Economic Association meeting, but pension-incentive programs may cost schools some of their most effective teachers. Separate studies of teachers in California, Illinois, and North Carolina paint a complex picture of the choice increasingly faced by education leaders: Keep your most experienced--and expensive--teachers, or encourage them to retire to ease budget woes. Illinois' 5+5 program allowed any teacher age 50 or older, and with at least five years of experience, to qualify for pension benefits immediately if he or she retired at the end of the 1992-93 or 1993-94 school year and paid a one-time fee. The average teacher who took advantage of the program had 29 years' experience, compared with incoming teachers who had on average less than three. Some middle schools even ended up replacing their exiting teachers with fewer teachers overall. Yet the less-experienced teachers did not lead to lower test scores.