Use more glue or pushpins to add fun mementos from their school days such as a tassel from a graduation cap, a copy of a locker key, a ticket from a special sporting event, or a dried flower from prom night.
Tassel Tree (Acacia) - Beautiful shrubs and trees, thriving in warmer countries, but a few grown out of doors do well in parts of England.
Keep the waistline loose and tunic like, and consider finding a top with more interest in the neckline with a tassel closure or long button placket.
If the tassel is a standalone favor, the string should be longer so it hangs on the edge of a shelf, dangles from a rearview mirror, or attaches to a key ring.
If you don't want to make a full tassel to add to a graduation cap favor, another option is to use a single piece of thicker string, such as satin cord intended for jewelry crafts, and fray the ends a bit to look more like a tassel.