If in Florida; we teach castanets in Jacksonville.

Christina made a very good point in her post. Castanets are not originally Flamenco but more Spanish folk and Spanish dance.
There are a few Flamenco rhythms where castanets can or may be used.

Sometimes people prefer to practice a bit of castanets on their own to accompany their dance, which can be fine.

However castanets are actually considered a musical instrument and proper or, let's say a more classical instruction can go up to 4 and 5 years.

Hope this is a bit helpful.... cast