This study investigated the quality assurance strategies and their relationship with teachers’ productivity in public secondary schools in Education District I of Lagos State. The descriptive survey design was adopted. The population of the study comprised 3,791 teachers of the 99 public secondary schools in Education District 1 Lagos State. Stratified random sampling technique was used to select 10 schools in the District based on the local government area while simple random sampling technique was used to select 300 teachers in the sampled schools. A self-designed questionnaire was used to collect data from the participants. Data collected were analyzed using descriptive and inferential statistics; percentage and frequency counts to analyze demographic data of participants and to answer the research questions. Pearson product moment correlation was used to test the formulated hypotheses at 0.05 level of significance. The result showed that supervision of school curriculum, use of instructional materials, regular assessments of teachers’ teaching records, educational training and development programmes for the teachers, and implementation of government policy to improve teachers’ performance all have significant relationship with teachers’ productivity in public secondary schools in Education District I of Lagos State. Based on these findings, it was recommended that quality assurance strategies must be put in place to improve teachers’ productivity and achieve positive result.