A clever forgery. Possibly the work of "The Mole" out of Reykjavik.
If you're not an experienced forensic document examiner, you probably don't posses the skills to see through this clever 5-year-old girl's near-flawless forgery of her mother's signature. You shouldn't feel bad though; it takes years and years of careful study to acquire an expert's eye. Let me walk you though this, though, so you can see where she tripped up.
First of all, notice that the "Y" is slanted to the left yet not dangling beneath the line. Most mommies will opt for one or the other. Also, see how the "O" isn't fully closed? Usually, a mommy will take more care when signing a school form. The big giveaway, though: Mommies tend not to think of "MOMMY" as their official name, regardless of what they're called around the house.