And yes, I understand the argument could be made, as the custodian it's your job to manage the tasks & time. Yes that is valid.
It's as equally valid as a service professional you would hope the client, principals, school staff would have expectations. That's where the principal creating a timed listing of a routine comes to play.
They know how their school runs, you may not. And yes you can know the general work, do okay. Better work is done having the details.
Quick example is doing bathroom cleaning & stocking. Say for example in hall A, the teachers let students out at five minutes after the hour for bathroom use of ten minutes. At five after nine to fifteen after nine AM then, you don't want to go try doing bathrooms on hall A.
On hall B they run bathroom breaks from ten minutes after to twenty minutes after. So you could take hall B first, hall A second and feasibly not get caught in a crush of students. Such details let you better manage your time and work, to prioritize.
And then at nine thirty you go get the breakfast trash from the cafeteria, then hall C. At nine forty you get the other remaining hall's breakfast trash. So by ten o' clock you can set up for lunches. At ten you then can go sweep the halls, dust lockers, check safety gear, check security. Ten thirty lets you go take a half hour lunch.
Again details the principals should know and be able to convey. You as the worker can then also look over the schedule, set up your own task based combinations and say shave up to an hour off the scheduled work simply because you can juggle two or more tasks in allotted times.
An example might be me going down through and dusting lockers while en route to check bathrooms. I could check safety gear visually, and in detail if needed while coming back to the cafeteria area, while also bringing that hall's trash down as well.
That lets you get "ahead", time for a bit of soma as me &
@SteveS45 discuss. The principals do not care either that you go sit down a bit. You've been doing the work, gotten caught up and ahead. They usually got nothing aside from needing you to be "available".
"Right boss, you know where I'll be. Sitting the custodian area, yep. Call on radio, have teacher come say something, I'm up and doing what's needed." And this is how things work out as wins for everyone. The work is done and a the worker feels good of their work, the people worked with, the environment of the work.
Happy workers make happy companies, make better product. In this case it's public schools. The schools stay cleaner, more fluidly organized, better situated to respond to any disruption/s, more capable of students given a stable education. As a plus students see people being courteous, communicating and striving for common goals, achieving. In short, there's harmony, balance.
I don't think I'm merely "talking out my ass" so to speak. Have lived and experienced a lot in life, have read up on a lot, learned from more experienced folks. Think it fair to say I got a good working knowledge of how to work and do so well. Don't think I' have cognitive bias in that, if so it's minimal as I try to always recall Strunk & White. "Author, remove yourself from the narrative."