Measuring Explicit Instruction Using Classroom Observations of Student–Teacher Interactions (COSTI)

Gunn et al. (2021) built a free tool called COSTI. COSTI stands for Classroom Observations of Student–Teacher Interactions.

The tool lists clear, low-inference markers like “teacher models the skill” or “students answer together.” Observers tally how often each move happens during a reading or math lesson.

The paper shows the steps to check that COSTI is reliable and valid. It does not give student scores or intervention results.

COSTI is ready for coaches to use when they watch lessons and give feedback.

Pasco et al. (2008) did the same thing for child communication. They built COSMIC, a tally sheet for intentional communication in free-play. Both tools use short checklists and reach high inter-rater reliability.

Jahoda et al. (2013) built the MAGIC scale for group CBT fidelity. Like COSTI, MAGIC predicts later outcomes, showing that simple fidelity counts matter.

Subramaniam et al. (2023) watched real K-2 math classes for students with IDD. They found only 61 % of math time was true instruction. COSTI gives coaches the lens to move that number up.

You now have a no-cost, research-backed form to show teachers exactly what explicit instruction looks like. Use COSTI during a 15-minute snapshot, share the tally, and set one clear goal for the next lesson. The tool works for any subject or grade, so you can fold it into your existing coaching cycle tomorrow.