Have the children each gather different colored leaves & a twig that can lay flat fairly easily. Each child should have about 6 or 8 leaves. Have him divide them into two piles. Now have him choose a color of construction paper & glue half of the leaves in a triangle shape; Putting stems on one side, all touching.  See examples in the photos below.

Do the same with the second half. These stems should be exactly opposite of the stems in the first batch. All stems should be touching. Last glue (teacher can use hot glue gun if desired) the twig atop all of the stems in between the leaf wings. Laminate & have fun!