Academic performance in Nyandarua Central sub-county has been dwindling for more than a decade now with no tangible cause got so far. Several educationists have been unable to unearth what ails it, mainly targeting teaching methods and improving them through Strengthening mathematics and science Education initiative, (SMASE), with no improvement and have left it to persist, prompting the locals to feel obliged to search for solutions to their problem. This study therefore sought to establish the influence of divorce on student's academic achievement in public secondary schools in Nyandarua Central sub- county, Kenya. The study was governed by Joyce Epstein’s theory of parental involvement in children’s academic achievement. The study used mixed methodology and concurrent triangulation design in data collection and analysis, by first clustering the twenty schools into day and boarding schools which have unique manifestation of extraneous causes and of non-performance in academics. The target population was secondary school students in public schools in this sub county are 12,800 of whom those that experience conflict at home number 4,661 and 960 parents and 600 teachers out of whom the sample was 270 students, 180 teachers and 240 parents. Data on performance was collected from progressive performance records of end tem examinations, while information on family conflict was gathered using questionnaires for students, teachers and parents and interview schedules for clarity and to increase response rate by busy respondents. Validity was done by the expert in the department and research. Reliability of the instruments was done by piloting and test retest administered Cronbach's Coefficient Alpha of 0.73 was realized. Quantitative data was analyzed descriptively by graphs, percentages, frequencies. The packages for social sciences (SPSS 22), whereas qualitative data was analyzed thematically, it was presented in narrative form. The results of this research showed an existence very high percentage 60% of administers agreed family set up influences academic achievement. The mean number of siblings of the respondents was 8.49 with a standard deviation of 1.37 siblings. A cumulative percentage of 91.0% of the respondents had up to 4 siblings. This implies most families have at most 6 members. The study concluded that the strong parental involvement is essential for educational progress and success. Consent of the respondets was sought. Based on the findings of the study the study recommended that: the society should strengthen family unit to reduce conflicts that pose challenges to pupil’s academic efforts. Parents should closely follow up children’s schools routines and coordinate with teachers, healthy dialogue, motivate and advice children on studies.