In an optimally efficient education system, all children enroll and complete the primary cycle in a one year to one grade ratio, acquiring basic reading, math and critical thinking skills along the way. Unfortunately, in many LMICs, particularly in Sub-Saharan Africa, many children entering primary school are met with limited instructional materials and under-equipped teachers (UNESCO, 2014), which can lead to education systems that are inefficient and characterized by low primary school completion rates, high grade-specific gross enrolment rates, and under-reported repetition rates, particularly in the early grades. This presentation reports the findings from a nationally representative study of over-enrollment and repetition in primary 1 in Uganda. The following research questions are addressed: 1) What is the enrolment pattern and the age distribution of pupils enrolled in primary 1, according to school records, teachers, and parents/guardians; 2) What is the repetition rate in primary 1, according to school records, teachers, and parents/guardians; 3) What is the relationship between repetition and age of enrolment in primary 1; 4) What is the enrolment rate in pre-primary education and its relationship with primary 1 repetition; 5) What are parents’/guardians’ attitudes and expectations about pre-primary education and repetition in primary 1. Data from enrollment, classroom, and administrative records on age and repetition were gathered from 120 schools. Caregivers and teachers of 1,440 randomly selected primary 1 students were also interviewed about student age, repetition in primary 1, and past enrollment in pre-primary education programs. Information from caregiver and teacher interviews was compared with data from enrollment, classroom, and school administrative records on the age of primary 1 students and repetition in primary 1. We also analyzed the relationship between participation in pre-primary education programs and student repetition in primary 1 through an odds-ratio logistic regression. Findings show that reports by caregivers and teachers of under-age and over-age pupil enrollment and repetition in Primary 1 were much higher than official reports. Additionally, pupils with no pre-primary education were 3.8 times more likely to repeat Primary 1, even controlling for gender, age at enrollment, and SES. Finally, almost 30 percent of caregivers enrolled their children in Primary 1 early, expecting repetition. Research and policy implications include the need to understand and challenge official repetition rates, to examine the effect of pre-primary on education system efficiency, and to investigate the effectiveness of automatic promotion policies.