It seems that either all of the schools have the same basic layout, or every anime producer got together and decided that the schools depicted in anime ought to be exactly the same. I've noticed this even with videogames so there must be some sort of connection to real life. And why does it seem that every protagonist has the second to last window seat and every classroom has the window to the left of the chalkboard (if facing the chalkboard). Even for classrooms on the opposite side of the hall, the window is always to the left. I live in the U.S. and no two schools have the same layout.
But I find it odd that multiple animation studios would use the same format. Hell, they even use the same bell tone for when classes begin and end. I was just wondering why all of the lockers are at the entrance to the school, arranged that particular way, large mailbox sized, stacked on top of one another, and back-to-back. I've never seen that sort of arrangement in the states. The school I went to, you had enough space to put all of your books, backpack, coat, and guitar in there if you wanted. These ones look like you can put a few books in there and some shoes and that's it.
General classroom layouts tend to be fairly similar, from what I understand, as do the class bell tones. But yeah, you might as well ask why the sound of crickets in your anime is always exactly the same clip. Because it is.
Maybe it is because it is familiar. That way they can convince the user easier that they are in class.
Bell ring tones are particularly not really different from each other im pretty sure of that as for the lockers japanese people doesn't really use lockers, and the lockers you see in front of school in japan is called a shoe locker so you shouldn't wonder why its only for shoes, I've also seen the lockers from the states yes its rather different and large that you could fit whatever you want to put in there
This is what most US schools used back in the day: http://www.youtube.com/watch?v=XIf2kjwhDQQ Sounds more like a fire alarm more than anything. The one I keep hearing in anime is the same chime my clock makes on the hour. Like this one: http://www.youtube.com/watch?v=xEQ3c8xyLZc ...except not that slow of a tempo. So I guess the point I'm making is that these similarities between anime is a reference to Japanese culture not just mere coincidence.