After-school programs have grown rapidly in recent years, spurred by rising employment rates of mothers, pressure to increase academic achievement, and concerns about risks to children who are unsupervised during after-school hours. The percentage of public schools offering "extended day" programs (which include before- and after-school programs) more than tripled from 1987 to 1999, from about 13 percent to 47 percent. The federal government's investment in after-school programs has grown rapidly as well. Funding for the 21st Century Community Learning Centers program, created in 1994, rose from $40 million in 1998 to $1 billion in 2002. The program now provides funding to 2,250 school districts to support school-based programs in 7,000 public schools. Some studies of after-school programs have found that these programs increase academic achievement and student safety, as well as reduce negative behaviors such as drug and alcohol use. However, other studies have found that after-school programs have no effect on--and even worsen--certain outcomes, leading to debate over whether the evidence supports increased investment in after-school programs. Four appendixes include response rates and data quality, study design and methods for estimating impacts, sensitivity tests and results for alternative specifications, and subgroup tables.