This paper uses four different datasets to describe the relationship between growth in enrolment and achievement as reflected by the number of pupils completing 8 years of primary cycle in Kenya who sit for primary exit examination known as Kenya Certificate of Primary Education (KCPE) and their performance in that exam measured in mean scores and z-scores. This growth in enrolment is associated with the introduction of Free Primary Education (FPE) policy in Kenya in 2003 as part of the movement towards realising universal primary education. It also analyses using regression method, the relationship between the performance in KCPE over time and growth in the number of pupils sitting for KCPE, after controlling for county factors such as level of poverty. Kenya has 47 counties which are its devolved administrative units.