The major literature review by Black and Wiliam (1998a) provided strong research evidence indicating that assessment for learning can produce significant gains in students' learning. The present study applied the main aspects of assessment for learning, as highlighted in the Black and Wiliam review, in a specific area of science education, that of graphs in investigation lessons. It is a qualitative study with ethnographic aspects aiming to look at the extent to which science teachers employ assessment for learning practices, when they teach and assess graphs. It involved close observation of nine science teachers for one school year, collection of marked copies of students' investigation reports, and two interviews with each of them. Two in-depth interviews were carried out with each teacher to look at how they teach and assess graphs, and how they help students. One interview (pre-observation), prior to the classroom observations and one upon completion of the observations (post-observation). They study found that only a few of the participant teachers implemented some aspects of assessment for learning practices. The contribution of the present study is that it exemplifies what good quality feedback in graphing skills looks like. It is argued that science teachers need professional support encouraging them to implement assessment for learning practices.