- Children’s early numeracy skills are essential for educational and professional success, but many children in low- or middle-income countries fall behind in developing these skills.
- Policymakers have tried to address this learning challenge by improving caregivers’ and/or teachers’ ability to teach numeracy, but more research is needed to understand what strategy is more cost-effective.
- An IDB study in Colombia shows that investing in either teacher or parent’s teaching ability significantly improved math learning but investing in both groups to address the same learning constraint did not lead to significant gains.
- This finding offers an important lesson for resource-constrained school systems seeking to design cost-effective policies.
When a child struggles with early math, where should scarce resources go—into helping parents support learning at home, or into training teachers to teach better in the classroom?
A new Inter-American Development Bank study in Colombia offers a surprising insight: implementing both approaches simultaneously may not be the most cost-effective strategy, particularly when investments in both teachers and parents are designed to address the same learning constraint.
Early numeracy skills strongly predict later academic success and even adult earnings. Yet in many low- and middle-income countries, children fall dramatically behind. In Colombia, only about 17% of students reached minimum math proficiency by the end of primary school in 2019.
A randomized controlled trial in the city of Manizales followed children from kindergarten into second grade to find out whether supporting parents or supporting teachers resulted in improved math learning. Each child was randomly assigned to one of four groups: a parental engagement program, a teacher training program, both, or neither.
The study evaluated these specific interventions and measured children's math outcomes through second grade.
Two Roads to the Same Destination
The first intervention reached parents the summer before first grade. Families received a workbook of playful activities built around household items—sorting bottle caps to count, setting the table to learn one-to-one correspondence—plus three text messages a week: a fact about child development, a practical tip, and an encouraging note.
The second intervention trained teachers over the first two grades of elementary school, through six workshops, weekly in-class coaching, and online support. First-grade teachers were trained in the first year and second-grade teachers the next, so children in these schools benefited from better-trained teachers across two consecutive school years. The training shifted teachers away from emphasizing rote memorization toward stressing active, hands-on learning that connects children's intuitions about quantity to formal math.
Though they targeted completely different people, both programs shared one philosophy: children learn math best by actively exploring patterns and quantities.
Each Program Worked, But Together They Didn't Add Up
Both programs, on their own, produced gains in math test scores compared to the control group. The size of the gains was comparable to other successful educational interventions.
Here's the twist: combining both programs produced no extra measured benefit. Children who received both improved about the same as getting just one. In this study, the two programs functioned more as substitutes than complements with respect to the math outcomes measured.
The gains were largest where they mattered most: on hard mathematical tasks, such as sequences, equations, word problems, where only 26% of children in the control group answered correctly. In this case, investing in teachers or parents produced almost the same size of improvement in math scores, suggesting that they were particularly effective in helping children develop more advanced mathematical thinking.
On basic skills like writing numbers, children in the control group already replied correctly to 87% of the questions, leaving little room to grow by the intervention.
The Bottom Line for Budgets
For policymakers watching every dollar, the cost numbers are revealing. The parental program cost just $20 per child, compared with $78 per child for the teacher program—about four times as much. Put another way, each dollar spent on the parental program delivered more than three times as much learning as a dollar spent on the teacher program.
trained teachers keep teaching new students year after year. Spreading that cost across future cohorts, the teacher program became at least as cost-effective as the parental one. The combined program cost more but did not generate additional improvements in the math outcomes measured by the study.
A Lesson in Focus
The central message is practical and slightly counterintuitive: concentrating resources on a single binding constraint—home or school—maximizes learning per dollar. The likely reason the combination didn't help is that both programs address the same underlying constraint.
This doesn't mean that there are no synergies between home and school investments; complementarities might emerge across broader skills or longer horizons. Additionally, a large body of education research highlights the importance of both family engagement and teacher quality, and additional benefits may emerge when interventions address different needs, outcomes, or stages of development.
But for governments deciding how to spend limited education resources, the study suggests a clear lesson: whether you empower parents or transform teaching, either path works—and doing one thing well may be the smartest investment of all.