Little Boards Skateboards has made it its mission to build professional skateboards for children. They use the same Canadian wood and deck shapes as the larger professional skateboards. They're just a bit smaller, in child-friendly sizes.
There's a lot on the market that calls itself a children's skateboard, but is actually useless junk.
Plastic wheels that barely turn, clunky boards made of 9-ply Chinese birch. That's cheap - yes, but it's not a skateboard.

Little Boards skateboards for children are equipped with IMAPCT trucks in the appropriate size and-tested ball bearings, and genuine, soft Urthan wheels. And because the boards are so good, they are our recommendation for children ages 3-8.
More information about sizes and quality can be found on the Little Boards Children's Skateboards website.