This piece of artwork is framed in the Yilan County Teacher's Center. The grade is not listed, but compared to the work around my Elementary school, I would peg this at the 3-4th grade level.
The captions read as follows, left to right (disputes on my translations welcome).
有小雞雞的長毛象 － "Has Little Chicken's Wooly Mammoth"
沒有小雞雞的長毛象－ "Doesn't Have Little Chicken's Wooly Mammoth"
小姐姐－"Little (Big) Sister"
The artist named the boy Chicken, his parts a "Wooly Mammoth", then drew two Wooly Mammoths (one in hat and scarf) with the corresponding parts.
Think of the implications of eternal return in this picture. The existence of a penis on a boy, and the absence of a penis, result in the literal manifestation of a figurative label for the genitalia. This manifestation produces its own binary, "wooly mammoth with a wooly mammoth" and "wooly mammoth without", a division which not only does not answer the sad question on 小雞雞's face, but demands further figurative representation (how do you represent a wooly mammoth's wooly mammoth and the absence of a wooly mammoth's wooly mammoth?).
小姐姐's left-dominant smile and lazy eye paint a picture of contented ignorance. I love 小雞雞's confused look. He seems a little jealous.