Define what an adjective is and have your students describe themselves at the beginning of the year. Collect and save 'til the last week of school and have them use adjectives to describe themselves now. Have they changed?
You could also use this as a "bucket filler" and have students write positive adjectives about their classmates on the back of their papers.
Even if you didn't pass these out at the beginning of the year, you can still use this for an end-of-the-year activity. Simply have students go back in time and recall how they felt.
Make this more of a keepsake by taking a first-day-of-school photograph, so children can glue it to the first section, as well as a last week of school photo, to glue on the other side. Instead of a photograph, you could also have students draw self portraits.