Anonymous left a link to the Australian Spelling Test, which was normed across 10,000 children in Southern Australia in 2004. I've just given it to C., who turns 15 at the end of the summer:
53 correct: above 15.5 yrs
more fun with Dick and Jane:
C.: "a - p - p - e - r - a - t - u - s"
me: "Wrong. It's a - p - p - a - r - a - t - u - s. With an e."
C.: So? It's a verb.
WTM on spelling programs
Schonell spelling test