This is a good way to assess your class. I do this in the beginning of the year to see how many letters and sounds they know. I put the date next to the number so I and the parents can see how long it took there child to learn there letters and sounds along with how much they learned in that time frame.
I also let the children color them when they know the letter or word. They like to be involved and they get more excited if they are the one coloring it and seeing there progress.