The evidence

Built on what the research actually supports.

We didn't start with a product and go looking for studies to back it up. We started with one well-evidenced idea and built the smallest tool that would carry it: short visits, one specific step, followed through.

Here's the research behind that — in plain terms, with the effect sizes translated into what they mean for kids. Principals matter. They matter by growing teachers. And teachers grow from one specific step, followed through.

Principals

A strong principal is worth about three months of extra learning — across the whole school.

The largest review of the evidence to date pulled together 219 studies from two decades of research. Its finding: replacing a below-average principal with an above-average one adds roughly three months of additional learning in reading and math in a single year (Grissom, Egalite & Lindsay, 2021). A great teacher changes one classroom. A great principal changes all of them.

And principals do it indirectly — mostly by developing teachers and protecting the conditions for good instruction. Stroll is where that work lives: who you coached, what you asked them to try, and whether it actually happened.

~3 months

of extra reading and math learning per year, across a whole school

219

studies synthesized across two decades of research

What leaders do

The leaders who move students are the ones who grow teachers.

When researchers compared leadership styles head to head, one pulled far ahead of the rest. Leaders who got personally involved in how their teachers learn had three to four times the effect on students of leaders who mostly set direction and inspire from the front (Robinson, Lloyd & Rowe, 2008). Of everything a school leader can do, being in the loop of teacher growth was the single biggest lever.

That's the part Stroll is built around — not the vision statement, but the next conversation and the next step.

3–4×

the effect on students when leaders are personally involved in how teachers learn

Coaching

Coaching changes classrooms where workshops don't.

Instructional coaching is one of the few forms of teacher support with causal evidence of improving both teaching and student learning. Across 60 rigorous studies, it produced real gains for students — on the order of two months of extra learning — alongside a marked rise in the quality of teaching itself (Kraft, Blazar & Hogan, 2018). The difference from a one-and-done workshop is the whole point: coaching is ongoing, personal, and tied to a specific change.

The active ingredient isn't the visit. It's the next step that gets done — which is exactly what Stroll's loop and follow-up queue exist to protect.

rigorous studies of instructional coaching, reviewed together

~2 months

of extra learning for students, alongside a marked rise in teaching quality

Feedback

Feedback makes teachers better — and it lasts.

Teachers who moved through a structured cycle of classroom observation and feedback got better during their feedback year, and stayed better afterward — worth about two months of additional learning for their students in the following years (Taylor & Tyler, 2012). The largest gains went to the teachers who had been struggling the most.

A walkthrough on its own changes nothing. Stroll turns it into one clear, concrete piece of feedback and keeps it in view with check-ins — so the loop closes instead of fading in the hallway.

Trust

Good coaching works by building teachers up.

A recent review spanning three decades found that when leaders lead instruction well, teachers' belief in their own effectiveness rises — one by one, and across a whole staff (Hallinger, Liu & Niu, 2025). That confidence is one of the quiet engines behind a stronger classroom.

Numbers don't grow teachers. Trust does. Stroll tracks change in teaching practice, never individual student scores. Data points the way. It never points the finger.

A note on the numbers

Honest approximations, not promises.

Researchers report their results in "standard deviations" — exact, but hard to picture. We've translated them into months of extra learning the way education researchers themselves do: by comparing each effect with how much a typical student learns in a year at the grade levels the study covered. One wrinkle worth being honest about — younger students cover more ground in a year, so a same-sized effect converts to fewer months in the early grades than it would in high school. Where a study spans several grade levels, we've used the conservative end. Every study is cited below so you can check the original.

And one line we won't cross: Stroll measures teaching, not test scores. The gains above are what the research ties to good coaching and steady feedback. Stroll's only job is to help you make that coaching and feedback happen — for every teacher, every time.

Sources

Check our work.

Grissom, J.A., Egalite, A.J., & Lindsay, C.A. (2021). How principals affect students and schools: A systematic synthesis of two decades of research. The Wallace Foundation.
Robinson, V.M.J., Lloyd, C.A., & Rowe, K.J. (2008). The impact of leadership on student outcomes: An analysis of the differential effects of leadership types. Educational Administration Quarterly, 44(5).
Kraft, M.A., Blazar, D., & Hogan, D. (2018). The effect of teacher coaching on instruction and achievement: A meta-analysis of the causal evidence. Review of Educational Research, 88(4).
Taylor, E.S., & Tyler, J.H. (2012). The effect of evaluation on teacher performance. American Economic Review, 102(7).
Hallinger, P., Liu, S., & Niu, X. (2025). Cultural context, principal instructional leadership, and teacher efficacy: A meta-analytic review, 1989–2024. Educational Management Administration & Leadership.

The method is how the research gets done.

Four rules that turn these findings into Monday-morning practice — with one of our walkthrough-aligned rubrics shaping what to look for.

Read the method Schedule a demo