Just wondering...

So I know it's summer but we all have those moments when we think about the school year, and we think what the fuck happened most of the time? Well I was wondering why teachers always conveniently have tests on the same day as your other classes! Like do they just pass each other in the teachers lounge and say "why hello Jim when are you having your test?" "Why hello Bob, I'm having mine on Wednesday!" "Well Jim I guess I'll have mine on Wednesday to!" Like what shit goes on that it happens so often? Now I might be wrong and it might just be coincidence, but if it's all the time? Well then Doctor Watson, I do say we have a conspiracy!