Why Are Fewer Boys Meeting Early Developmental Milestones? What the Latest Research Really Tells Us

In our recent blog exploring school readiness — and the striking statistic that 37% of children were not ready for school in 2025 — we highlighted a growing concern shared by schools across the country: more children are arriving in Reception without the foundational language, social‑emotional, and self‑regulation skills they need to thrive. Early years settings are working incredibly hard to close these gaps, yet the pattern is becoming clearer year on year.

Alongside this wider picture, practitioners frequently tell us something else they’re noticing: boys are disproportionately represented among the children who are not meeting early developmental milestones. Whether it’s language, attention, social interaction, or self‑regulation, boys are more likely to be flagged as “behind” — and this trend is visible long before they reach school.

So today, we’re digging deeper into this question. Why are fewer boys meeting developmental milestones in the early years? And more importantly, what does this mean for our practice, our environments, and the way we support children’s development from birth to five?

The answer, as always, is nuanced — and far more hopeful than the headlines suggest.

⭐Key Takeaway: Boys often develop differently, not deficiently — and our practice needs to reflect that.

A Clear Pattern in Early Childhood Development

Recent research consistently shows sex‑based differences in early development:

• A 2026 cohort study found 47.4% of boys fell into “low” developmental trajectories compared with 7.3% of girls.

• A 2024 study of 800,000 children revealed boys typically reach many milestones later than girls — and that mixed‑sex milestone charts over‑diagnose delay in boys and under‑diagnose delay in girls.

• International studies show girls tend to score higher in language, fine motor, and social‑emotional domains.

This doesn’t mean boys are “behind.” It means boys often follow a different developmental rhythm — one that traditional milestone charts don’t always capture accurately.

Why Are Fewer Boys Meeting Milestones?

1. Biological and neurological development

Girls’ brains mature slightly earlier in areas linked to:

• language

• social‑emotional processing

• self‑regulation

Boys show more variability in these domains and are more likely to experience neurodevelopmental conditions such as autism or ADHD. This creates a wider spread in developmental timing.

2. Milestone charts aren’t always sex‑specific

Most milestone charts were built using mixed‑sex data. When we apply one curve to everyone:

• Boys appear “delayed” more often

• Girls’ subtle delays are easier to miss

Sex‑specific charts provide a more accurate picture and reduce unnecessary referrals.

3. Environmental and social influences

Adults often interact differently with boys and girls:

• Boys receive more physical, active play

• Girls receive more verbal, nurturing, conversational interaction

These differences shape early language and social‑emotional development.

What This Means for Early Years Practice

At Growing Together Early Years, we champion relational pedagogy, responsive environments, and developmentally attuned practice. This research reinforces what many practitioners already know intuitively.

1. Boys need language embedded in movement

Rich language experiences should be woven into:

• outdoor play

• construction

• role play

• sensory exploration

Not just sit‑down conversations.

2. Girls need careful observation too

Because girls often meet milestones earlier, their quieter struggles can be overlooked. Sex differences shouldn’t distract us from seeing the individual child.

3. Milestones should guide, not define

Milestones are helpful markers, but they’re not a verdict. A child’s wellbeing, relationships, curiosity, and engagement tell us far more.

4. Early support should be proactive

If boys are more likely to fall into lower developmental trajectories, early years environments should intentionally strengthen:

• language and communication

• social‑emotional connection

• self‑regulation

• problem‑solving through play

This isn’t about “fixing boys” — it’s about meeting them where they are.

A More Nuanced, More Hopeful Story

The headline “boys are less likely to meet milestones” can sound worrying. But when we dig deeper, the story becomes far more encouraging:

• Boys often develop differently, not deficiently

• Girls’ needs can be overlooked if we assume they’re always “ahead”

• Sex‑specific research helps us refine our practice

• Responsive, relational environments support all children to thrive

The real takeaway? Children flourish when we understand their unique developmental rhythms — and when we create spaces that honour those rhythms with curiosity, compassion, and connection.

That’s the heart of Growing Together Early Years. And it’s exactly where this research leads us.

References

1. Sex‑specific neurodevelopment trajectories (2026) Zhang, Y., et al. (2026). Sex-specific neurodevelopmental trajectories in children under three years: A retrospective cohort study. Journal of Child Development Research.

2. Sex‑specific milestone attainment (2024) Barzilay, E., et al. (2024). Sex-specific developmental milestone attainment from birth to 6 years: A population-based study of 800,000 children. Pediatrics.

3. Cross‑country early development differences McCoy, D. C., et al. (2016). Early childhood developmental status in low- and middle-income countries: A meta-analysis. Child Development.

4. Social‑communication differences in toddlers Constantino, J. N., et al. (2020). Infant and toddler social communication sex differences and early neurodevelopmental risk. Nature Human Behaviour.