Project STAR
Tennessee's Project STAR (Students-Teacher Achievement Ratio) was designed to determine the short- and long-term effects of small class size in grades K-3 on student performance.

Phase 1: 1985-1989. K-3 classes of 13-17 students were compared with classes of 22-26 students. Findings:

• Students in smaller classes substantially outperformed students in larger classes on both standardized and curriculum-based tests. This was true for white and minority students as well as inner city, suburban, and rural schools.
  
  
• In smaller classes, fewer students were retained in-grade, and there was earlier identification of struggling students.

Phase 2: Lasting Benefits, 1989. This study began as a follow-up to the STAR study to examine if the effects of smaller class sizes stayed with students once they returned to larger classes.

Findings:
In fourth grade, students from smaller classes still outperformed students from larger classes in all subjects and were better behaved.

Phase 3: Project Challenge, 1990. Based on these findings, Tennessee began phasing in smaller classes in grades K-3 in the poorest districts.

Findings:

• These districts moved from near the bottom of school district performance in Tennessee to near the middle in reading and mathematics for second grade.
  
  
• In-grade retention was reduced.

Update
In 1999, researchers reported that the effects of small class sizes in grades K-3 lasted all the way through high school. Students from small classes are:

• More likely to graduate from high school on schedule and less likely to drop out;
  
  
• More likely to have enrolled in honors classes and to graduate in the top 10 percent of their class; and
  
  
• More likely to take SAT or ACT exams, indicating that they plan to go on to college. Further, the black-white achievement gap is reduced by 56 percent for black students who began school in small classes.

Researchers also found that students in small classes in grades K-3 were between six and 13 months ahead of their regular-class peers in math, reading, and science in each of grades 4, 6, and 8. Researchers reported that for the benefits to be sustained through later grades, at least three years in a small class are necessary. In addition, the benefits of having been in a small class in the primary years increase from grade to grade. 

Student Achievement Guarantee in Education (SAGE) Program
SAGE began in Wisconsin in 1996 by phasing in class size reduction in grades K-3 in school districts serving high-poverty students. The aim is to achieve a student/teacher ratio of 15:1.

Findings:

• SAGE first-, second-, and third-grade students performed consistently better than comparison students in mathematics, reading, and language arts on the Comprehensive Test of Basic Skills.
  
  
• First- and third-grade, African-American SAGE students gained significantly more than SAGE white students, closing the achievement gap. The achievement gap widened for non-SAGE students.
  
  
• Teachers reported more individualization in their instruction due to fewer discipline problems; being more knowledgeable about each student; and having more enthusiasm for teaching.

It should be noted that while SAGE findings are consistent with Project STAR findings, SAGE schools were also required to implement a rigorous academic curriculum, provide before and after-school activities, and implement professional development programs and accountability plans. 

Rouse Study
The Milwaukee Parental Choice Program is a publicly funded voucher program. In her study, Rouse compares the achievement of Milwaukee voucher students and students in three types of Milwaukee Public Schools: regular schools, magnet schools, and schools participating in the Preschool to Grade 5 Grant Program (P-5 schools). P-5 schools serve "predominantly minority and extremely disadvantaged" children and receive supplemental state funds that have enabled them to cut their pupil-teacher ratio to 17 to 1 on average. Findings:

• Students in the P-5 (small class size) public schools made "substantially faster gains in reading" than those in the regular public schools, the public magnet schools, and the voucher schools.
  
  
• Students in the P-5 (small class size) public schools made faster math gains than students in the regular public schools and the public magnet schools, and the same gains as the voucher schools.

Wenglinsky Study
Educational Testing Services (ETS) researcher Harold Wenglinsky compared 1992 fourth- and eighth-grade NAEP math results to class size and other policy initiatives. For purposes of the analysis, Wenglinsky defined small class size as fewer than 20 students.

Findings:

• Fourth- and eighth-graders in small classes performed better than those in large classes, even when taking into account demographics, resources, and cost of living.
  
  
• Fourth-graders were one-third of a grade level ahead of their peers from large classes; eighth-graders were one-eighth of a grade level ahead.
  
  
• The largest gains were found for inner-city students: fourth-graders were three-fourths of a grade level ahead of students in large classes.

Class-Size Reduction (CSR)
During the mid-1990s, the California Legislature passed the Class-Size Reduction (CSR) incentive program, which provided funds to schools statewide that set class size to 20 students in grades K-3.

The $1 billion initiative was signed just six weeks before the start of the new school year. Even though the program was voluntary, there was significant pressure from parents and the press to reduce class size. By the end of the first year, 88 percent of first-graders were in reduced classes along with 57 percent of second-graders.

Due to the program's design, it is unclear how much effect the initiative has had on raising student performance, resulting in some officials questioning the cost-effectiveness of the program. Although researchers are unable to attribute achievement gains directly to CSR, California's efforts to reduce class sizes provide important lessons for education officials trying to implement small classes in their states and/or districts.  CSR researchers point to a variety of reasons for the inconclusive results:

• CSR in California was associated with declines in teacher qualifications and an inequitable distribution of qualified teachers. CSR caused an immediate need for 20,000 new teachers in a very small period of time. To meet the demand, teacher certification requirements were "relaxed" resulting in an influx of un- and under-prepared new teachers. In addition, qualified veteran teachers were taking advantage of the new vacancies to leave less advantaged districts for more desirable positions in more affluent districts.
  
  
• CSR was offered in every school instead of targeting funds to disadvantaged schools. This "one size fits all" approach with funding resulted in wealthier districts that already had smaller classes receiving an initial boon of funding, while overcrowded districts were forced to dip into their general funds to cover shortfalls.
  
  
• Funding was inadequate. CSR provided $650 per student compared to the $2,000 per student provided for the SAGE program.
  
  
• Serious problems associated with overcrowded schools were ignored.
  
  
• No trial program was conducted to explore various class-size reduction options.
  
  
• The adopted definition of small classes (20 students) directly contradicted prior evidence and experiences of other states.