Math coaches, specialists, and student achievement: Learning from the data 

Given the ineffectiveness of traditional, whole-group, one-shot professional development workshops (Ball & Cohen, 1999), many school districts have, in recent years, turned to instructional coaches to support the teaching and learning of mathematics (McGatha, Davis, & Stokes, 2015). However, coaching is expensive (Knight, 2012), especially when experienced  teachers are removed from the classroom to serve as coaches (Mangin, 2009), and additional research is needed to better understand whether the benefits of coaching outweigh the costs.   

In theory, coaching should be an effective professional development model, since coaches can meet with teachers multiple times throughout the school year, closely observe their teaching practice, and help them address specific problems and challenges they face (Desimone & Pak, 2017; Gibbons & Cobb, 2017). As yet, though, little large-scale empirical research has been conducted into how well this model actually improves student achievement. Most studies of this topic have been small-scale and qualitative in nature, and few researchers have conducted large-scale, quantitative studies of the relationships between coaching and student achievement (Hjalmarson et al., in press; Saclarides et al., in press). 

One group of studies has shown some promising results, suggesting that math coaching was related to student gains (Balfanz, MacIver, & Byrnes, 2006; Campbell, 1996; Foster & Noyce, 2004). In these studies, however, the coaching was part of a larger school reform initiative, making it difficult to tease out the extent to which the coaching itself — and not some other part of the reform —made a difference.