Although school-based assessment (SBA) is a well established assessment practice in many countries, its use has been limited in Hong Kong until recently. When the scheme was extended to HKCEE English Language, it was faced with strong opposition. Many teachers felt that they did not understand the scheme and were negative about its use and increased workload. With a view that any change in education is a process that involves people and thus its success depends largely on the perception, readiness and implementation of the people who actually carry out the change, a study is proposed to examine teachers' perception, readiness and uses of the SBA scheme. A total of ninety-five Hong Kong teachers who taught HKCEE English Language from twenty-one schools were invited to complete a questionnaire based on a revised Stages of Concerns Questionnaire (SoCQ) and among them, eight teachers were selected to participate in an in-depth semi-structured interview to explore their perceptions, uses and evaluations of the scheme and to gauge their Levels of Use (LoU) in the innovation. The findings indicate that the teachers did not give the scheme a high priority in their teaching work although many had quite strong opinions to offer. In general, they had high early concerns (informational, personal and management concerns) and the concerns profile was similar to that of nonusers and early users. The in-depth interviews show that the majority of the interviewees had proceeded beyond routine use, including two teachers who had run the scheme for only one year. It also finds considerable variations on the way the SBA scheme was operated and a few practices were in violation of the SBA criteria set by the authorities. Implications for teachers, policy-makers and researchers on school innovations arising from findings are discussed.