Alphabet Knowledge

As you know, I have been implicating the Handwriting Without Tears program in my classroom. During the week we do a letter activity every day whether it's writing the letter, sharing our letter bags, letter searches, etc. However, I'm noticing that some children still aren't remembering the letters we've learned. After five letters we do a review week and go over all of the letters, but this still isn't helping.

How can I increase their letter identification skills of previously learned letters? Again, I am trying to meet standard RF. PK. 1a I can recognize and name some upper and lowercase letters in the alphabet and can name the letters that are in my name. I have worked in small groups with children and practiced a identifying a few letters. I sometimes need to tell the child the letter and they will repeat it. Then, when we go back to the letter and I ask again what the name of the letter is he/she will forget. Is this an issue with short term memory or are they just not grasping identifying letters with letter names?