Virtual Stock Market apps suitable for teens?

[generallypreoccupied]

DS (13) has been asking lots of questions about the stock market and wants to dive in start trading. It's not something I know much about, but I can see there are some virtual trading apps out there that might do the job of educating him without financial loss.

Does anyone have experience with these and a suitable recommendation?

A book recommendation would be helpful too.

We'd be really interested in this too so bumping post!

There's an excellent book by Peter Lynch called One Up On Wall Street which is a good start. Don't know about the app though - be a great business idea!