From the study: "Teachers work more than they are required to work by contract, but less than self reported hours of work. I find that teachers are more likely to overestimate their hours of work in the CPS than workers in other occupations, and conclude that this is likely because of an uneven work year".

Even by your own example, you're only at 35 hours a week, and that's before you subtract out the weeks of summer vacation, winter vacation, spring break, etc; where the workload is certainly far less than 40 hours a week.