Per week I'd guess you'll only actually need to plan 4-5 classes and then just repeat them to different sets of students.

But I'd guess it'll just involve the regurgitation of 1 lesson/week to a particular grade, senior 1 or senior 2, not senior 3 as they will be in their final year of middle school before undertaking their college entrance exams at the end of the academic year. Even more boring than you say, but less prep, and no end-of-term oral exams for students.

Likely, it's one of those key middle schools as the salary is above average for that kind of work. I guess more will be expected of the job encumbent than would be at a run-of-the-mill establishment of that kind.

There'll probably be suggestion boxes on each floor for students who wish to point out to the headmaster how he (or she) can advise teachers how to improve their teaching. Not for me, such a set-up. I've already experienced that, and prefer more freedom and more job security re my teaching. Less money, yes, but virtually no stress at an average public county senior high.