Coronavirus (COVID-19) outbreak affected educational systems worldwide, leading to widespread and lengthy closures of educational institutions. The containment measures of COVID-19 put in place interrupted learning, nutrition, and equal access to digital learning portals and led to rising cases of child labour, drug and substance abuse, and teenage pregnancies. This study aimed to establish the effect of containment measures for COVID-19 on participation of students in secondary schools in Machakos County, Kenya. It was guided by the Classical Liberal Theory of Equal Opportunities and the Production Function Theory. Descriptive and correlational research designs were adopted. The population for the study was 93,204 respondents comprising 296 principals, 5,920 teachers, 86,979 students, One County Quality and Standards officer (CQASO), and Eight Sub-County quality and Standards Officers (SCQASO). Proportionate and simple random sampling were used to obtain 382 respondents, including 195 students and 89 teachers. Also sampled purposively were 89 principals, one CQASO, and eight SCQASOs. Study instruments included questionnaires for principals, teachers, and students, while an interview schedule was designed for CQASO and SCQASO. The tools were subjected to reliability and validity tests before use. Face, content, and construct validity were ascertained before administering the instrument. Reliability was computed using the Cronbach Alpha coefficient on the data obtained from a pilot study in Kitui County, an average reliability coefficient of 0.816 obtained ascertained an acceptable reliability threshold. Qualitative data were analyzed thematically. Hypotheses were tested using simple linear regression statistics at α = 0.05 significance level. The study's findings established containment measures for COVID-19 affected participation in public secondary schools in Machakos County. The study recommends the establishment of computer studies as a core subject to equip learners with technological know-how for use in case of disrupted learning leading to the abrupt closure of schools.