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Don Hackmann, Education, (515) 294-4871
Cathy Curtis, Education, (515) 294-8175
Kevin Brown, News Service, (515) 294-8986


AMES, Iowa -- Student achievement may be impaired by certain models of block scheduling, according to a new series of studies by Iowa State University and ACT.

Block scheduling models typically divide the school day into 80-90 minute blocks of time. The two main models are 4x4-semester plans (four classes per semester) and eight-block alternating-day approaches (eight classes throughout the year, with four classes on one day and four other classes on the next day). In contrast, under the more common seven- or eight-period daily scheduling models, students typically attend seven or eight 45-50 minute classes each day.

Block scheduling is used by about 30 percent of high schools in Iowa and Illinois, according to a series of joint studies conducted by a research team of Donald Hackmann, associate professor of educational leadership and policy studies at Iowa State, and Matt Harmston, Ann-Maureen Pliska and Robert Ziomek from ACT Inc. ACT is an Iowa City-based educational services firm that administers the ACT Assessment. The ACT assesses high school students' general educational development and their ability to complete college-level work.

One of the joint studies conducted in conjunction with the ACT staff investigated changes in ACT composite scores for 568 public high schools in Illinois and Iowa, including longitudinal data for the two years prior to the implementation of block scheduling and four years after. This study showed that schools using the 4x4 semester model had markedly lower ACT scores in the first few years following implementation.

Schools using the eight-block, alternating-day approach experienced slight declines in ACT scores, while schools using the traditional eight-period day showed little change in achievement.

Rural schools in both states using the 4x4 semester method fared especially poorly in the study. The first years after implementation showed a marked decline in ACT scores, with a slight rebound in the fourth year. Eight-block, alternating-day schools showed a slight drop in ACT scores.

Suburban schools and urban schools demonstrated somewhat similar results, but the numbers of these studied were small, making interpretation of the data more difficult. In all cases, the decline in average student composite ACT scores after implementing the schedule change was beginning to level off after four years.

The study indicated that the flexibility of block scheduling should be balanced by the potential impact on student achievement and that school's need to carefully monitor student achievement over several years following a move to block scheduling.

"Over time, school faculties may become increasingly proficient with creating hybrid models and slight modifications of these blocks, finding effective ways to schedule alternating-day blocks and/or daily periods without the 4x4 structure," says Hackmann. "Furthermore, a one-size-fits-all approach to scheduling may not be the ideal model. Some disciplines may be better suited for larger instructional blocks, while learning in other subjects, such as foreign language, mathematics, and Advanced Placement courses, may be better facilitated through some type of year-long approach."

Hackmann noted that some high school faculties consider block scheduling because some research indicates that the programs may enhance school climate, improve interaction between teachers and students, reduce disciplinary referrals and suspensions, and improve student attendance. Teachers also may prefer larger blocks of class time to promote in-depth exploration of content, provide for more hands-on activities, and allow teachers more flexibility to differentiate instruction.


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