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Block scheduling or blocking is a type of academic scheduling used in schools in the American K-12 system, in which each pupil has fewer classes per day. It is more common in middle and high schools than in primary schools. Each class is scheduled for a longer period of time than normal (e.g. 90 minutes instead of 50). In one form of block scheduling, a single class will meet every day for a number of days, after which another class will take its place. In another form, daily classes rotate through a changing daily cycle.[1]

Blocks offer more concentrated experiences of subjects, with fewer, usually half as many if going through a schedule transfer, classes daily.


Under a traditional American schedule, pupils in a high school will study seven subjects a day for 45 minutes for each day of the week for a semester. There will be two semesters in the year so 14 subjects could be studied. Some pupils will not study all seven subjects. There was great variety as each school board was free to decide the requirement.[2]

Traditional Scheduling
Time Semester 1 Semester 2
Before 09:45 Sports training some electives
09:45 – 10:30 Government Economics
10:30 – 11:15 French French
11:15 – 12:00 Geometry Geometry
12:00 – 13:00 Lunch
13:00 – 13:45 Computing 1 Computing 2
13:45 – 14:30 Biology Biology
14:30 – 15:15 English English
15:15 – 16:00 PE PE[2]

Conversion to block scheduling became a relatively widespread trend in the 1990s for middle schools and high schools in the United States. Prior to this, many schools scheduled classes such that a student saw every one of their teachers each day. Classes were approximately 40–60 minutes long, but under block scheduling, they became approximately 90 minutes long.[citation needed]


Many forms of block scheduling were devised.[2]

Alternate day block scheduling

Also referred to as A/B block scheduling, Odd/Even block scheduling, or Day 1/ Day 2 block scheduling. Students take three to four courses, around 90-120 minutes in length, per day all year long on alternating days resulting in a full six or eight courses per year.[3][4] An example table of a possible schedule is provided below.

A/B Block Scheduling
Time A Day B Day
7:30-9:00 Math English
9:05-10:35 Spanish Computers
10:40-11:25 Lunch
11:30-1:00 History Science
1:05-2:35 Physical Education Health

4x4 block scheduling

Students take four courses, around 90 minutes in length, every day for the first semester and take four different courses every day for the second semester. This results in a full eight courses taken per year.[3][4] An example table of a possible schedule is provided below.

4x4 Block Scheduling
Time Semester 1 Semester 2
7:30-9:00 Math English
9:05-10:35 Spanish Computers
10:40-11:25 Lunch
11:30-1:00 History Science
1:05-2:35 Physical Education Health

2 core 2 electives

Another common block system exists in which students spend up to 100 minutes per class, and earn four credits each semester. Excluding very rare occasions, students at schools using this system take two core classes and two electives per semester. Some schools modify this system further to use one of the mid-day periods for students to take optional year-long classes (usually band) that take half of the period length and take another year-long class during the rest of the period (such as math or journalism). Under such a system most of the classes taken on a year-long basis have all students participating, however it is not uncommon for journalism or yearbook classes to operate under the normal system and only have a few students who leave or arrive halfway through the period. It is also not uncommon for these classes to be scheduled as two credits, and taken both semesters.[citation needed]

2 Core 2 Electives
Time Semester 1 Semester 2
08:30 – 10:00 Band Band
10:00 – 11:30 French 1 French 2
11:30 – 12:00 Lunch
12:00 – 13:30 Science 1 Math 1
13:30 – 15:00 English 1 History 1

Waldorf blocking

Waldorf schools traditionally employ a mixed approach. Certain academic subjects are taught in intensive three to five week blocks known as main lesson blocks, while other subjects are taught in regularly meeting skills classes.[5]

Colleges and universities

Within the context of post K-12 establishments, such as in medical school or other intensive university program, a block schedule may mean taking one class at a time, all day, every day, until all of the material is covered. A normal university course might then be completed in three or four weeks of focused effort on a single topic. This is sometimes called "One Course At A Time" ("OCAAT") (see Colorado College and Cornell College). When used as a supplement change instead of the normal schedule, this approach is sometimes called a mini-mester.[citation needed]


"Where we were able to combine data to produce summary effect sizes, we found that 4 x 4 block scheduling resulted in higher cross subject achievement than traditional schedules. However, the outcome average cross-subject achievement could conceal worsening performance in some subjects and better performance in others."[6]

Some schools have compensated for this by making AP courses last for the entire school year, providing essentially double the instruction time of normal classes, but this results in a dramatic reduction in the number of courses a student can take. Some schools that make AP courses year long offset this by having students always choose a pair of AP courses during class registration. The student will go to the first AP class one day, and the other AP course the next day. Therefore, the student takes the same number of courses as other students, but both AP classes last for the duration of the year.[citation needed]

A systematic review on Block Scheduling was also conducted by Dickson et al. (2010) at the EPPI-Centre which asserts that there is no conclusive evidence to support the introduction of policy guidance on the use of block scheduling in secondary schools in the UK. Although the findings do not indicate that participating in block schedules would produce negative outcomes for pupils across subjects, neither are the positive effects of block scheduling strong enough to recommend their implementation.[7]


Some critics believe that certain subjects suffer from a lack of daily exposure to subject matter and practice that occurs with an A/B block schedule. Courses like mathematics, foreign languages, and music may benefit from daily practice and suffer from a lack thereof.[8]

Block scheduling can result in gaps of a day or days (or even weeks or months in some circumstances) where students are receiving no reinforcement of instruction in a specific subject like math or history, and critics say this results in retention problems and the need for more remedial review.[8] Some observers similarly feel that summer vacation has a similar effect of interrupting the learning and retention process forcing a need to repeat material at the start of a new school year in the Fall.[citation needed]

A University of Virginia study of 8,000 college students found that students who had block scheduling in high school performed worse in university science courses.[1]

Students who miss a block-scheduled day can miss a considerable amount of material in a single subject, possibly making it more difficult to catch up. One way this can be mitigated is by making course material available online, which allows students to catch up outside of school, and another way is by using a flipped classroom system.

Some students are better able to manage their time with nightly homework in every class, while other students do better with larger homework assignments that are spaced out over several days. Some subjects may benefit from daily drills while other subjects may lend themselves to less frequent homework projects. Mid-term transfers between schools with different schedules can be problematic in cases where the schedules are different.[8]

See also


  1. ^ a b "Block scheduling: Not helping high school students perform better in college science" Archived January 23, 2008, at the Wayback Machine by Robert Tai
  2. ^ a b c H, Natasha. "What Is High School Block Scheduling? Block vs Traditional Schedules". Owlcation. Retrieved 28 August 2017.
  3. ^ a b Trenta, Louis; Newman, Isadore (Fall 2002). "Effects of a High School Block Scheduling Program on Students: A Four-Year Longitudinal Study of the Effects of Block Scheduling on Student Outcome Variables". American Secondary Education. 31: 54 – via EBSCOhost.
  4. ^ a b Lewis, Chance W.; Dugan, James J.; Winokur, Marc A.; Cobb, R. Brian (December 2005). "The Effects of Block Scheduling on High School Academic Achievement". NASSP Bulletin. 98: 72–87 – via EBSCOhost.
  5. ^ Trostli, Robert (January 2001). "Main lesson block teaching in the Waldorf School" (PDF). Research Bulletin of the Research Institute for Waldorf Education. 6 (1). Archived from the original (PDF) on 2007-11-05.
  6. ^ "Block Schedules and Student Performance on AP® Examinations" (PDF). The College Board. May 1998. Archived from the original (PDF) on July 27, 2011.
  7. ^ "What is the effect of block scheduling on academic achievement? A systematic review". EPPI-Centre.
  8. ^ a b c "The Case Against Block Scheduling" by Jeff Lindsay