This paper highlights patterns in school enrollment indicators that affect the efficiency and effectiveness of education systems in a set of low-income countries: those that have expanded access quickly in the last decade or two, but have not yet absorbed that expansion efficiently. Although the patterns in these indicators are observable in the first few years of schooling, they could constitute a cause of low learning outcomes at the end of primary school. The data show strong empirical relationships between an early primary enrollment bulge, low levels of pre-primary participation, and poor performance on early grade cognitive skills. This work does not attribute causal precedence to these patterns but instead argues that the indicators are reflections of each other, constituting a ‘‘knot’’ of issues undermining the foundations of the affected education systems. The article presents some of the cost implications and suggests that many countries are already paying for pre-primary education without realizing it.