In a varied career, Dylan Wiliam has taught in urban public schools, directed a large-scale testing program, served a number of roles in university administration, including Dean of a School of Education, and pursued a research program focused on supporting teachers to develop their use of assessment in support of learning.

Dylan is well known for a major review of the published research evidence on formative assessment which he co-authored with Paul Black in 1998, titled Inside the Black Box. Since that time, Dylan has worked with groups of teachers and leaders all over the world on the topic of developing formative assessment practices. He has written several publications and professional articles.