English Phonemic rules for plural /-s/

Dear Dave's ESLCafe,

I had an interesting tangent with my student last night. He's an advanced student from Russia. We got to English plurals/3rd person present verb agreement.
He wanted to know what the exact rule was for [-s], [-z] and [-ez].
I told him that I wrote this out ten years ago in a Morpho-phonology class in college, but couldn't remember all the details.
He asked if all Americans learned this rule in high school, and I chuckled, "of course not". He was surprised, cause all Russians learn all their complex morpho-phonological rules by 6th grade.

Anyone have a simple write-out of that plural/verb [-s] rule?

Thanks

Chris
ChrisESL.blogspot.com

1) If the final sound of the original word is alveolar (s, z, sh, zh (as in leisure, ch or j (as in John) the pronunciation is [iz]:
e.g. watches, bosses, galoshes, glasses

2) If the final sound is voiceless, other than the sounds above, the pronunciation is [s]:
e.g. cats, books

3) If the final sound is voiced (including all vowels), the pronunciation is [z]:
e.g. dogs, birds, bees

Works for third person -s on verbs too.

Students need to be reminded to look at the sound and not the letter in case they think capes is pronounced "cap-es".