Most public schools in Kenya post poor results amid claims that parents are not supportive of their children’s educational activities at school. While research has shown that parental involvement in primary schools is a significant contributor to the mental capacity, social and cognitive behaviour of students, public primary schools in Ainabkoi sub-county are yet to achieve. This paper draws our attention to a study that was conducted in the sub-county to investigate the relationship between parental involvement in pupils’ educational activities at school and their academic performance in public primary schools. This study was guided by Type 3 Epstein’s model of the six types of parent involvement as developed by Joyce Epstein. The study adopted ex-post facto research design and considered a target population of 2404 Class 8 pupils and 61 class teachers from which 331 Class eight pupils and 61 teachers were drawn using stratified random sampling and census approach, respectively. Questionnaire and interview schedule were used for data collection which was later analyzed using descriptive and inferential statistics. Descriptive statistics were analyzed in the form of percentages and means. Chi-square was used to test the hypotheses of the study. The found out that there was a positive and significant relationship between parental participation in educational activities at school(X2=22.619; p=0.001) and pupils’ academic performance in Ainakboi Sub County. Qualitative data were analyzed using a thematic framework. The study concluded that parental involvement in educational activities in school was positively related to academic performance. The study recommended that the government should sensitize parents on involvement in their children’s school activities through policy development to improve their academic performance.