Within-School Exchangeable Rosters and Randomization Blocks
RCTClinical Trial
Field experiments in public school systems cannot randomly reassign teachers across different schools or non-certified subjects without violating administrative, labor, and credentialing constraints.
Picture this
Instead of shuffling players across an entire sports league where positions and rules differ, organizers only swap players between teams that play in the same division during the exact same match time, ensuring fair substitutes without breaking the game schedule.
What the evidence says
668 randomization blocks were successfully formed across 284 schools. Standard deviation of baseline student sorting across classrooms within these blocks was 0.382 to 0.520 prior to randomization, demonstrating that blocked randomization successfully eliminated substantial pre-existing within-school student sorting.
- Who was studied
- 2,462 teachers requested across 316 urban public schools; 1,591 teachers randomly assigned rosters across 668 randomization blocks in 284 schools.
- How
- Blocked randomized controlled trial grouping teachers into exchange groups based on subject certification, grade level, and common open class periods.
What to do
Restrict random assignment blocks in educational field experiments to subset groups of instructors sharing identical grade, subject certification, and schedule period availability.
From the source
"We call these groups of teachers 'randomization blocks.' Schools then constructed rosters of students for the randomization blocks and submitted them to the study team. Within each randomization block, analysts at the RAND Corporation randomly assigned each of the rosters to the participating MET project teachers."
Have We Identified Effective Teachers? Validating Measures of Effective Teaching Using Random Assignment