The School Questionnaire was administered as part of the 2017-18 National Teacher and Principal Survey (NTPS), which is a state and nationally representative sample survey of public and private K-12 schools, principals, and teachers in the 50 states and the District of Columbia. The selected school samples include about 10,600 traditional and charter public schools and 4,000 private schools. This Data Point examines the characteristics of public schools in the United States where students attend classes fewer than 5 days per week. In an effort to attract high-quality teachers and to reduce costs, some schools and districts have been reducing the student school week to four days. Despite the increased use of this strategy, there is little substantive research that examines the effect of a shortened school week on students. Skeptics have indicated concerns with lack of access to meals, the impact on families' child care needs, and student performance.