Complex sentence: On the helmet is a plate that the helmet rests on it says, the old helmet, the one school stole it from the other they both agreed on whoever wins gets the helmet, but if the other school wins the next year they get back.
Split into simpler sentences: On the helmet is a plate that the helmet rests on it says, the old helmet, the one school stole it from the other. They both agreed on whoever wins gets the helmet, but if the other school wins the next year they get back.