In the US, replacing free play with formal instruction for very young kids seems to have backfired. 

The idea seems obvious: Starting sooner means learning more; the early bird catches the worm.

But a growing group of scientists, education researchers and educators say there is little evidence that this approach improves long-term achievement; in fact, it may have the opposite effect, potentially slowing emotional and cognitive development, causing unnecessary stress and perhaps even souring kids’ desire to learn.

this approach improves long-term achievement; in fact, it may have the opposite effect, potentially slowing emotional and cognitive development, causing unnecessary stress and perhaps even souring kids’ desire to learn.