Performance-based tools to assess school readiness domains such as Approaches to Learning are lacking in Low and Middle-Income Countries such as Kenya. This study aims to develop the Kenyan version of the FOCUS app (Finding Out Children's Unique Strengths), a game-like computer tablet assessment of two Approaches to Learning domains: mastery motivation and executive functions. We used a design-based research approach to develop and validate the FOCUS app, initially designed for the US and Hungarian Cultures, to suit the Kenyan context. We later followed children longitudinally from preschool to grade 1, to assess the applicability of the FOCUS app to the two grade levels. Results showed that the FOCUS app is valid and reliable. There was no significant difference in mastery motivation between the two waves. The FOCUS App can complement other school readiness tools to assess Approaches to Learning as one of the strategies to enhance school and life success.