This article explores changes in teachers’ knowledge of the cognitive demands of mathematical tasks following their participation in the ESP ‘‘Improving Practice’’ workshop throughout the 2004–2005 school year. The article also examines how those changes connect back to teachers’ experiences in the workshop. The findings reveal that at the end of the ‘‘Improving Practice’’ workshop, ESP teachers significantly increased their knowledge of the cognitive demands of mathematical tasks and had significantly higher knowledge than teachers in the contrast group. The author concludes that the strong connections between changes in teachers’ knowledge and their experiences in the workshop provide indications that learning occurred during the workshop, and this learning may have influenced subsequent changes in teachers’ classroom practices.