How well must you be a pianist to play a concerto?

It really depends on the concerto that you are wanting to play. If you are trying the Grieg Piano Concerto in A Minor, then you will need to be willing to put up a lot of work, and you would still probably have trouble, but if you wanted to do a Beethoven Piano Concerto, then you might be able to do it. Just ask your teacher weather or not she knows any concertos that you might be able to play at your level, but I think that the Mozart Concertos will come up, because you've been playing for 10 years. Also, just try the music at home, and see if you can play it then ask your teacher weather she would like to hear the piece that learned on your own. Most teachers will like the fact that you can learn music on your own, because that is what they are supposed to eventually get their students up to. here's a link to ALL of the Mozart concertos, and more.

http://imslp.org/wiki/Category:Mozart,_Wolfgang_Am...

It is under Piano Concerto, so look under "P".

I'd say you need to be at least grade 8 ABRSM to attempt any concerti. I got grade 8 with merit but I'm still not good enough to play any!

Your teacher does not sound like they hate intelligent questions, so why not ask her?

I would guess, without having a real sense of the BUSINESS of grade levels, that your question now is general, and I would say that the idea of playing a concerto is a good goal.

p.b.