This is my biggest complaint Op and echoing you and Pps.
IT drives me insane esp with math and science. Dd was doing fractions some wonky way and having trouble with it so I tried to teach her my way (I guess considered "old school"...and I'm a FCPS product myself), but to no avail. Then she was trying to figure out the difference between solution and solventS in science and I had to Google it on my phone (!!!) to help explain it bc there was no explanation with her homework packet. I could go on.
I can see how some upper grade subjects could, in theory, eliminate textbooks bc the subject gets outdated so quickly by the time the textbook is edited, goes to print, approved by the admin, and finally distributed throughout the school system, but ES and MS subjects where the info is fairly standard really need textbooks.