Where does it go?

Okay, today and this year have been quite frustrating in the homeschooling realm of things. My oldest has had to step up to the plate this year and really study and really make her brain work (I guess the other grades have been too easy). She hasn't liked any of it. She is still making mostly A's and some B's but she has had to work hard at it everyday that we do school (Not to mention that I have to work hard at studying Pre-algebra, history, science, and more and encourage her along even when I know she hates every minute of it right now).

Now my middle child is that, somewhere in the middle. This year however he has managed to make straight A's except for one B the first semester. He has truly stepped up and did all his work.

But my youngest I'm at a loss. I don't understand how she could manage to get to the third grade, easily at a 4 or 5th grade reading level, understand basic mathematical calculations, and yet forget the rest. I don't understand.

Let me give you an example. In first grade you teach your kids what a noun and what a verb is right. Well she could always quote to me verbatim the definition of those two. Recognize the noun and verb in a sentence, etc. In second grade you do the same thing and now in third grade your adding more along the other parts of speech (helping verbs, adjectives, etc). So every year it astounds me that we will be floating along and she gets it right one day and then the next she will wake up and do school and will look at me as if she had never heard those words before?!

I'll ask what is a verb?
I don't know mommy.
We've gone over this before, "A verb is a word..... now you finish it"
Takes the place of a ...... noun maybe?
AAAAAAAAAGGGGGGGHHHHHH!

Now for first grade I would understand this forgetfulness and maybe given a stretch second grade, but third grade no way. So on we go. All of November and December was given to verbs, verb phrases, action verbs, state of being verbs, etc. Everyday it was a new challenge to see what she retained. Some days she got it perfect and other days you were speaking a foreign language to her.

So today, she has a quiz. Now mind you we've had quite a bit of down time and a tragedy in our family. But her not remembering what we covered for two whole months (and collectively three years running now), astounds me. Today it was:

Review: Isabella what is an action verb? I don't know mommy? Maybe like, "Sarah was playing outside." and "outside" is the verb? (telling me in an asking voice and watching my face to see my reaction). No! Isabella that is not an action verb. Holding the broom, I said, "If I was to do an action right now what would it be?" "Sweep!" she said! Yeah, then I said, "give me some action verbs. After a minute of silence, I said, "give me some action verbs that you would do." I don't know mommy was her response. AAAAAUUUUUGGGGGHHHHHH! I covered my face and prayed at this moment that He would help me.

Where does it go? I mean she gets it one day. I do audio, visual, and kinesthetic things with her for all her subjects and this isn't the only one this happens with. Its like the "brain fairy" takes it out of her memory bank for a day or two just to see my reaction and then puts it back in. I don't understand how a very bright child can just "forget". But she does. How does someone who knows how to read not remember what a verb is?

Okay, just wanting to vent a little and see if anyone else out there is shaking there head in understanding as well.