Just think - IF something goes wrong and you violate any regs, who will be held responsible? If you passed Air Law and be solo, you are supposed to know. If you haven't passed, why did the flight school let you out alone? I did not dig in the regulations, because it does make absolutely sense to have certain exams passed before solo-ing. At the school I passed PPL and started to learn to fly, you had to have passed all theory exams before solo. At least the insurance of the plane will be quite interested in such things, may there something had happened ...