Here in Singapore they can participate in a playgroup starting 18 months, the weird thing is most of the time it's in a classroom type of environment.

Our daycare has a bunch of "school-esque" stuff. It's almost 100% learning through play, but the kids do have development plans, areas that they focus on learning, etc. "School" is a broad term, and while sitting at a desk is 100% unrealistic for a 2 year old, opportunities for educational play definitely exist.