Jasper by Adam Davidson & Andrew Pollard
From the original instructions...
You are Eric, a troublesome schoolboy, and your task is to steal your report card out of the school safe in the staff room so that you don't get into trouble! To do this, you must collect the combination letters for the safe and write them on a blackboard - not such an easy task seeing as one letter of the four letter combination is held by each of the teachers in the school. In order to get them to tell you their letter, you must make all of the shield scattered around the school flash by hitting them or firing your catapult at them. Once all the shields are flashing, knocking the teachers over with your catapult will cause them to tell you their letter of the combination. All except old Mr Creak, that is, who is so old he cannot be trusted to remember his letter. It has been hypnotically implanted in his mind and he will only remember it when he sees the number of the year that he was born!
To make things even harder, the school is teaming with kids and teachers and you are expected to attend lessons! Einstein is a swot and will tell on you if you do anything naughty, Angelface is a bully and will try and get you into trouble, and Boy Wander is a harmless rogue who loves to write on blackboards! Do anything wrong or be in the wrong place at the wrong time and you will be given lines! Collect over 10000 lines and you will be expelled from school!
Some shields are easy to reach, but others will require you to invent more ingenious methods of making them flash. Once you have your report, the chase isn't over as the flashing shields attract the attention of the teacher's to your crime! This means that you must then turn them all off again in order to complete the year! And then there's next year....!