“…For example, in a most recent study with longitudinal data on middle school math teachers and students in a mid-western state, a recent study (Akiba, Wang, & Liang, 2015) found that one hour increase in school average amount of teacher participation in professional conference and informal communication was associated with on average a .15 point increase and .23 point increase in the annual growth rate in students' math scores. The significance of teacher PD on student learning has also been broadly documented by researchers around the world such as in England (Wood & Bennett, 2000), Australia (Ingvarson, Meiers, & Beavis, 2005;Kettle & Sellars, 1996), Norway (Kallestad & Olweus, 1998), Pakistan (Warwick & Reimers, 1995), and Israel (Angrist & Lavy, 2001). Despite these empirical studies, the knowledge base on the impact of PD on educational outcomes is still not as strong as it should have been (OECD, 2005;Yoon, Duncan, Lee, Scarloss, & Shapley, 2007).…”