DAR ES SALAAM, Feb. 6 -- AT around midday, just outside many secondary schools in Dar es Salaam, something quietly revealing happens. During breaks, students do not rush to the football field or gather in loud clusters as they once did.

Many sit in small groups, eyes fixed on glowing tablet or mobile phone screens for those schools, which allow. Fingers swipe. Heads nod. Laughter erupts at videos adults will never see. This is not mischief.

It is the new normal. For todays children, social media is not an activity. It is an environment. This is why Australias decision to bar children under 16 from major social media platforms has stirred debate far beyond its borders.

While the policy was made in Canberra, its implications reach classr...