I read some of the reviews where some users didn't have sound. For what it's worth, I have not updated to iOS6. I am still on iOS5 and it worked fine for me. I only wish that there are more levels, more vocabulary and increasing levels of difficulty.
If you have very young students, this is a fun learning game for the students to play. It costs $1.99, though I purchased it during the Chinese New Year celebrations when it was on sale at half price -- for only $0.99.
Check it out at
https://itunes.apple.com/us/app/piggy-picnic/id412674857?mt=8