This paper investigates the teaching strategies used by secondary school science teachers in Swazi schools that perform well in national examinations. The performance of learners in science in these examinations is generally low, as indicated by the public examination results published by the Examinations Council of Swaziland. However, a few schools have persistently performed very well over the years. This study sets out to identify the perceptions of teachers in high-performing schools on effective teaching strategies in science and to determine the teachers' actual classroom practices. The study is framed by the classification of effective science teaching strategies developed by Schroeder and colleagues, and by the effective curriculum implementation theory by Rogan and Grayson. The sample comprised all teachers in the 12 schools that performed well during the years 2011-2014 in Junior Secondary School Science, and Senior Secondary School Science Biology and Physical Science. Data were collected through a questionnaire (n = 77) and classroom observations (n = 25). The frequencies with which teachers identified and implemented specific strategies were determined. The results showed that science teachers in high-performing schools were clearly knowledgeable about effective teaching strategies as reported in the literature. However, many of the identified strategies were minimally implemented by the teachers and in most cases, implementation was at a low level of cognitive demand, yet high-performing schools should exemplify the best practices for other schools to emulate. It is suggested that teachers be continually oriented for implementing the demands of any existing curriculum.