The instrument in the flute family most often used by students is the C flute, so named because it is pitched in the musical key of C. Many children learn on a C flute, but small children who want to start learning may need a smaller flute that is easier to hold and control. The size of the child, his familiarity with other instruments and his interest level in learning should help you determine which type of kids' flute to choose.
Small children who have trouble holding and handling a standard C flute might benefit from a beginner's flute made from wood, or even a plastic fife. This will help the child become familiar with holding a flute-like instrument without having to handle one that is as long and heavy as a standard flute. Kids younger than eight may benefit the most from this kind of beginner kids' flute.
An older child who can easily control a standard-sized kids' flute should probably learn on a C flute. Total beginners may benefit from a lip plate that has a slight curve, as those are easier to blow into properly. Most teachers also recommend a closed-hole flute that has solid keys. When the child presses the keys, the hole is completely covered. This is the standard style found in most band rooms and is especially appropriate for beginners.
An open-hole flute has holes in the keys that also must be properly covered by the fingers when the keys are depressed. Professional flautists often prefer open-hole flutes because they can get a range of nuance with each note that cannot generally be achieved with closed-hole instruments. If a child is serious about the flute, some open-hole kids' flutes are available that come with plastic plugs in the holes. This allows the child to learn on a closed-hole instrument, which many believe is easier. The plugs can be removed as the child progresses without the need to purchase a second instrument with open holes.
Kids' flutes typically have a nickel-silver finish which looks nice and gives the instrument a pleasing tone. Nickel-silver instruments may not have the same tone quality as professional silver flutes, but they can generally stand up to less careful treatment and are recommended for kids. A nickel-silver flute can later be upgraded with a silver headjoint, for students who become serious about their musical studies. This is less costly than a silver flute, but allows the flute to approach that warm, professional tone.
Any kids' flute will be an investment. Many schools and music stores will rent instruments to students who want to try an instrument. This may be a good option when it is unclear how long the child will be interested in playing. Purchasing a used instrument is also a less expensive option. A music teacher or someone with knowledge of instruments should inspect any used kids' flute for flaws, and play it to make sure the pads, keys and lip plate are in good condition.