Ask a group of Japanese under the age of, say, thirty-five if they'd had lessons--what the Japanese call narai goto or o-keiko--when they were very young, and you'll probably find most, if not all, did. Having been in the Eikaiwa (English conversation) trade for many years and having personally taught many preschool and elementary school aged children, I know from experience that Japanese children maintain schedules that would have American kids on their knees, crying, "Uncle!"
The whole business of training, cultivating, and educating children would be one to research some day. In the meantime, here are the results of a half-arsed survey I did the other day.
Of the twenty university sophomores (18♀/2♂) that I surveyed, 17 had had lessons of some kind before starting elementary school. By the time they had enrolled in elementary school, all of them were taking some kind of lesson. The most popular lessons were piano (15), swimming (13), calligraphy (11), and English and cram school, i.e. juku (10). Asked if they would also send their own children to these kinds of lessons, 19 said yes. The type and number of lessons they would like their children to take, however, changed.
I've long been interested in knowing not only what people studied and when, but also whether they feel they had benefitted from the lessons and whether they would do the same for their own children. Most, it appears, feel they did and would make their future children do likewise.
As a father myself the time will come soon enough when I will be forced to decide if I will make my own son take these kinds of lessons and what I will have him study. I am already leaning towards lessons in a third language, guitar, calligraphy, soccer, abacus, and swimming. The poor kid.