In many developing countries, researchers and policy makers have downplayed issues of age in grade intentionally. This is done partly to avoid the pedagogical issues that over-age or under-age children in schools raise. It is also done to avoid putting extra pressure on government especially in developing nations that is still working hard to achieve and maintain universal enrollment targets. However, age-in-grade incongruence cannot be ignored as it has implications for pedagogy and child development. The purpose of this study was to evaluate the degree of congruence between student-age and grade placement in the basic or compulsory education phase of the education system in one African country, Botswana. Contrast was made between grade placement practices at school and the Age-in-Grade placement policy of the country. Using data from the 2011 National Census, and adopting a survey research design, involving the entire population of 587,308 children still in basic education in 2011, the paper found high levels of incongruence between the actual grades in which students were in, and their age appropriate grade level. Lesser than 30 percent of the 7-13 year old still at school in the compulsory education phase was in their age appropriate grade. The population of learners in the basic education phase was either one or more grade levels ahead (or behind). Incongruence persisted across various demographic categories including citizenship, gender, and main language spoken at home which suggests the school system did not discriminate. None of the 28 Census Districts in the country had the majority of the population in the compulsory education phase in their expected grade level. There was gender variation in the age-in-grade incongruence. Compared to boys, more girls entered the compulsory education system early. More boys entered school over-aged. Likewise, compared to non-citizens, more citizens entered compulsory education over-aged, or at the right time. The evidence suggests a flouting of the age-in-grade policy, and points to systemic challenges such as drop out, repetition and re-enrollment which needs urgent attention. The paper theorized that the age-in-grade incongruence is indicative of chronic problems in the education system which in the long run can adversely affect education access, curriculum implementation, and educational attainment. Various implications for curriculum implementation and grade placement policy design have been discussed.