The aim of this study is to analyse the success of School Based Assessment (SBA) implemented in 2010/11 in Malaysia. It examines teachers' readiness, confidence level and enjoyment in teaching mathematics. It also investigates if participation in SBA professional development courses impacted on teachers' readiness for it. A total, of 260 teachers (65 males and 195 females) were selected as respondents while 12 teachers were interviewed for their feedback. The findings show= that the teachers involved in the study have a low level of readiness and confidence in implementing SBA. Professional development courses related to SBA did not have any impact on teachers' readiness level. More than two-thirds of them reported that they did not enjoy teaching since the implementation of SBA. This study indicates more effort is needed to enhance teachers' competency in achieving the goals of SBA.