And as noted above, many if not most music kids play at least some piano. I do think the piano has a really different focus, though; while a few kids do play in jazz or other ensembles, it is generally a much more solitary instrument. So I think it really depends on your/your child's goals for learning an instrument.
Yes, piano is a solitary instrument, so something else to consider.
I have a different take on the piano as a "solitary" instrument. Yes, it's solitary when learning for the most part, because you practice at home typically rather than in a group. However, for kids who really get into piano, there can be group opportunities down the road - accompanying concert or jazz band, playing in a small group, etc. More important though, of all the instruments you can learn (with the possible exception of guitar), a piano can be an extremely "social" instrument once you've learned enough to be able to just sit down and play - when you're hanging out with friends, etc - you can play. Most other people can't! When people want to sing, you can accompany them. I'm not explaining this well lol... but for example, playing clarinet in band is truly a group experience. Most kids don't continue with concert band in college. Some do. Very few adults continue playing with a concert band throughout their lives - and rarely, if ever, when hanging out with friends or just hanging out at home with family, do adults just whip out a clarinet and play. But if there's a piano around and you want to play, you can play. Other people usually enjoy listening or singing along. You don't have to haul your instrument everywhere with you, but keyboards and pianos just tend to "be" places.
Re what to actually choose for a starter instrument, I'd recommend the piano also (but not because it's a social instrument lol)... because it offers the opportunity to build a solid foundation in music understanding, which will benefit a child no matter what instrument they choose to play later on.
And... from what I've seen (having seen quite a few kids start instruments early)... many kids who start playing a brass or woodwind early on change their minds about which instrument they really want to play when they get into middle school and band/orchestra starts in school.
polarbear
