The main objective of this paper is to investigate the optimal age category at which primary school pupils
from low income families perform their best in literacy at grade 6 level. Age is a potential learning barrier
because of its link to cognitive development as well as its influence on interactions between pupils
within classrooms. The sample consisted of 7041 grade 6 pupils, spread in 226 schools across six major
urban slums in Kenya. Using descriptive statistics, we examine the distribution of grade 6 pupils’ age. We
then examine incidences of over-age pupils and incidences of grade repetition across various subgroups
of pupils disaggregated by factors such as sex, wealth background, grade repetition, school type and
geographical location. Finally, using multilevel techniques, we estimate the pupil age category that has
greatest positive impact on literacy achievement at grade 6 after controlling selected pupil and school
factors.
Irrespective of pupil sex, grade repetition, wealth background, school type or geographical location
the results indicate that grade 6 pupils perform their best in literacy when they are in the age category
ranging from 10 years 6 months to 11 years 5 months. The results also indicate that, in general, younger
pupils were likely to achieve better than older pupil in literacy regardless of the background under
consideration. Implications of the findings for policy and practice as well as further research are outlined.