Final answer:
Stephen might have come home from school with his arithmetic book broken.
Step-by-step explanation:
Based on the given information, it is not explicitly mentioned what exactly Stephen came home with broken. However, since the excerpt mentions him taking an old arithmetic book from the shelf and going to school, it is possible that his 'arithmetic book' is what was broken.
Arithmetic is a branch of mathematics that deals with the properties and manipulation of numbers. It includes topics such as addition, subtraction, multiplication, division, and more.
In this case, Stephen's arithmetic book would be a resource for him to learn and practice these mathematical operations.