Is the brightness set at whatever point the last user had the brightness set at? So if student 1 logs on and sets the brightness to the dimmest, does it stay that way until student 2 logs in a changes it?

@jouwstrab no, it goes back to dim. Say it starts dim with no one logged in. Student 1 gets in, increases brightness. They log out, it's dim again. Student 2 logs in, increases brightness...logs out, dim again. Etc

Still no resolution. I even talked with an Apple tech in our area. He suggested carrots...good for the eyes

In fact, it's now gotten worse. Where before it was only a few in the cart of 30, now every single one behaves the same way. The rest all started doing it at the same time, and it was about a week after updating them (so I doubt it's the update because it would have been immediate, right?)

Did you ever have a resolution to this issue?

We now have this issue, did anyone come up with a solution please?

For what it is worth, our problem was the screen protectors we had on the iPads.  They were coving up the sensor by the camera.  I used a hole punch in that spot and the problem is now gone.

Thanks, @krausec I might give that a shot too... It's defo a case issue even though we are using a 9th gen case! Where exactly is the light sensor?

It is right next to the camera on the top.  The best test, pull your screen protector back from the top and see if the screen brightens up.  Once you pull it back you will see the sensor next to the camera.