When you say grade 3-4, do you mean RCM Canada?
If so, I would suggest Arabesque, op 100 no 2 by Friedrich Burgmuller.
Nice piece, large range. Lots of runs. Fun piece. At a competition I heard it at least three times.
Also try Melody by Robert Schumann. About Grade 2-3.
If you're looking for other pieces, all of the pieces here at pianostreet.com have a grade level next to them. You should be able to find a nice selection from there.
Hope it helps!