Put your head of year's car up on bricks.
Order substantial pizza, taxis, takeaway, locksmiths to the school at lunchtime.
Get hold of a builder's account details at your local builders' merchants and order very expensive building items to be delivered to your school, e.g. bricks, cement mixer, etc.
Phone up a clown and tell him to come into school on the last day. Leave, so he demands money from someone else.