Anything goes for materials--fruits, flowers, leaves (folded artfully as you see here), popsicle sticks, pencils...
First Form students (grade 7) generally make fairly small and simple arrangements. By the time they're in Form 6 (12th grade), they can be quite elaborate.
Just as a note of contrast--the students who won the director's prize for knowing soccer trivia were just as proud as the winners of the flower judging.
