Run an old-fashioned spelling bee as a home room competition at lunchtime. Promote it with signs filled with spelling mistakes. Host it by grade level for each day with Friday as the finals for school champ.
The words are made known to the audience by placing them on a screen behind the participants, so the whole cafeteria can see the correct spelling.
The grade winner for each day gets a can of Alphagetti. Home made trophy for the champ with a mini box of Alpha Bits. The words do need to be challenging, so a long list is needed for each day.
Preston High School