I must be old
None of my teachers had laptops.
In fact, there were only 2 Apple ][+'s and a ][e in the entire school.
They still managed to teach me history, economics and (amazingly) computer science.
But then, they weren't using facebook...
Ok cheap shot - I have sympathy with the teachers, but I fail to find a particularly compelling reason to use a laptop in the classroom. In which case, use your own and a usb stick to plug into a school computer. BYO computers are probably not forbidden, just forbidden to be plugged into the network - which is a common corporate policy.
Better yet, don't use one at all. Handwritten material and a photocopier is all you need. You could go further, make the students hand-write everything. Perhaps they would then plan their work first. If anyone complains, point them to the school policy of not providing the required equipment and the superiority of a decent textbook over wikipedia as a teaching tool and cribbing source.