The study was designed to assess changes in farmers' knowledge of farmer seed production through schools (FSPSs) in Vietnam. A set of 25 questions covering five technical areas of the seed production process was used for pre and post knowledge testing at 12 FSPSs in the provinces Binh Dinh, Nam Dinh, Nghe An and Dong Thap. The main findings show an overall increase in farmer's knowledge scores after attending the FSPS. FSPS-farmers with low scores on the pre-field school test (ex-ante) scored much better on the post field school test. Gender had no effect on the test scores. Binh Dinh province had significantly higher mean scores on the post field (ex-post) school test compared to farmers in Nam Dinh, Nghe An and Dong Thap provinces. The increase in knowledge score is linked to the application of good practices learned in the field school as farmers who applied good quality seeds, low seed rates and the transplanting method showed a large increase in scores. The results of this study indicate that the tests provide insight into the knowledge gaps. (Contains 7 tables and 4 figures.)