spelling websites, testing for grades 1-9?

[Fishkram]

I am looking for a website (maybe free, maybe a pay site), that would have a grade level appropriate words. The software would say the word and the kids would type it. I am not really interested in creating my own list, but would like my sons to improve their spelling on a wide range of words.

Has anyone have good experince with a site or could recommend one? I am looking at spellquizer.com, but not sure the lists you can download have a relative grade level with them. Would hate to be too high of a level and have my younger son get frustrated that he doesnt know 8th grade words when his is only in 5th grade.

Thanks for the help.