Effectiveness of In-Service Training Programmes on Teachers’ Instructional Quality in Public Senior Schools in Mavoko Sub-County, Machakos County, Kenya

The purpose of the study was to examine effectiveness of in-service training programmes on teachers’ instructional quality in public senior schools in Mavoko sub-county, Machakos county, Kenya. The study focused on the following research question: How do in-service training programs affect teachers’ instructional quality in public senior schools in Mavoko sub-county? The study was grounded in Human Capital Theory by Theodore Schultz. A mixed-methods approach under a convergent design was employed. The quantitative component adopted a cross-sectional design, while the qualitative component was guided by a phenomenology design. The target population comprised 16 public secondary schools, including 16 principals, 285 teachers, 2,850 Form Three and Four students, and one Sub-County Director of Education. Sampling techniques used included stratified sampling for schools, simple random sampling for teachers, systematic sampling for students, and criterion-purposive sampling for principals and SCDE sampling, resulting in a sample of 7 schools, 7 principals, 74 teachers, 285 students, and the Sub-County Director of Education. Data collection instruments included questionnaires for teachers, interview guides for principals and the Sub-County Director of Education, focus group discussion guides for students, a document analysis guide, and an observation guide. Quantitative data were analyzed using SPSS version 28, where descriptive statistics such as frequencies, percentages, means, and standard deviations were used. Inferential statistics, including t-tests and ANOVA, were used to determine differences between variables. Findings were presented using tables. Instrument validity was ensured through face, content, criterion, and construct validity, while reliability was tested using Cronbach’s Alpha (0.8). Qualitative data were analyzed thematically using NVivo, guided by credibility, dependability, transferability, and confirmability, with ethical considerations observed. The study found that successful in-service training programs enhanced teachers’ pedagogical skills, instructional strategies, assessment practices and classroom management. It implies that continuous professional development contributes significantly to the enhanced instructional quality of teachers. The study recommends that education stakeholders should strengthen regular needs-based training programs, provide adequate resources and establish monitoring mechanisms to ensure sustained improvement in teaching practices in public senior schools.