The word "sat"

JoJo has finally mastered his letter knowledge and I have started to get him into being able to recognize simple words. I decided that the words that end in "at" would be a good place to start. So I made up some little cards for him with all the words that end in "at". He just needed to figure out the beginning sounds. He was very excited to be given his cards to practice and we sat down to go through the words one by one. I tried explaining how each word rhymed and he just had to put the first sounds together. I guess this really did not make sense for him because after going through the list of words twice, he still seemed confused. Here is an example.....
I hold up the word "sat"
me: "What word is this?"
JoJo: sssssssssssssss
me: "now add 'at' to the end"
JoJo: " bat"
me: "No, it starts with the 's' sounds
JoJo : "snake"
me : "No silly!"
JoJo : " rug, kite, chair"
me: "come on JoJo, you know this!"
JoJo " rat, fat, hat"
me : "NO! It is sat! with an 'S'!!
JoJo: "Oh"

I am sure I just sprouted a gray hair after that encounter.