This study used a concurrent mixed research design to examine the extent of quality assurance practices implementation in West Kenya Union Conference secondary schools. Purposive, simple random, and convenience techniques were respectively used to identify 160 respondents from 7 accredited and two non-accredited schools (84 teachers, 9 principals, 4 BoM members and 57 students from form 3 and 4) and 6 education directors from Conferences and Union. Questionnaires, open-ended, and interview guides were used to collect data. The general systems, developmental systems and thinking systems theories were employed to underpin the implementation of QAP. The descriptive statistics shows that the extent of implementation and effectiveness of quality assurance practices were to a moderate extent. Although there was a positive linear effect between the predictor variables and the effectiveness in QAP; the Pearson product moment correlation coefficients showed a moderate positive relationship with the dependent variable. In research question four, failure to follow institutional strategic plan was the highest predictor affecting the implementation and effectiveness QAP. The researcher postulated a theory leading to the paradigm ‗Effective Implementation of Quality Assurance Practices‘ (EIQAP) to fill the gap in the implementation and effectiveness. The study findings revealed that quality assurance practices were not effective due to inadequate implementation. The EIQAP has six competencies: transparency, delegation, timely empowering and equipping implementing teams at all levels with accountability and prompt feedback. Cost benefit analysis be done for effective implementation of QAP, adopt and improve on the contextualized instrument for frequent evaluation and test the EIQAP model for workability.