Using longitudinal elementary school teacher and student data, we document that students have larger test score gains when their teachers experience improvements in the observable characteristics of their colleagues. Using within-school and within-teacher variation, we further show that a teacher’s students have larger achievement gains in math and reading when she has more effective colleagues (based on estimated value-added from an out-of-sample pre-period). Spillovers are strongest for less-experienced teachers and persist over time, and historical peer quality explains away about twenty percent of the own-teacher effect, results that suggest peer learning.EdWeek provides further detail on the study methods here, which is helpful since there's a fee to read the full report.
It makes sense that teachers would routinely glean use of some basic ideas from one another, and that there would be measurable good results when a new colleague has particularly helpful thoughts to contribute.
To me, that looks like the baseline level of interaction that happens more or less naturally.
How much more can happen as teachers move up from that starting level to more robust, intentional, systematic collaboration fully focused on raising performance? Because, in the end, that's what professional learning communities do: the members learn from one another deliberately, consistently, and with powerful results for students.