Firstly, the school district already has a picture of every child at the school. Second, they already track the child (manually) at all times throughout the day.
So, they are not collecting any more information than they already had, nor are they collecting any more information than is legally required (attendance tracking is likely to be legally mandated)
The end result is the same exact data exposure / privacy risk that they started with, and more classroom hours to actually teach instead of taking attendance.
The classroom setting is a particularly good example of the narrow use case when facial recognition is acceptable. Unlike, for example, in a retail establishment, where a casual customer who browses the store but does not buy anything would otherwise remain anonymous.
Quite the contrary, you do not want anyone in the classroom who is anonymous.
As part of my job, I had to be able to recognise and put a name to all of my students. This is legitimately difficult and I spent a lot of time doing it. However, it was not for doing attendance! If you are in a school system below university and your teacher doesn't recognise you or know your name... I mean... I can't even comprehend what a bad situation that is. How could you ever teach a student if you know so little about them that you can't even recognise them? When you are marking their paper and see their name, if you don't even know who they are, how can you give appropriate guidance? That kind of situation would be shocking. And to be fair... because it is really, really hard I know a lot of teachers who have no clue... but seriously, this is not what we aim for!
Once you know the students, attendance is easy. Why is that chair empty? Who is supposed to sit there? Look at your seating chart (seriously, it's the best way to learn their names...). Is that person anywhere else in the room? No? They are absent. Mark it on your list. That takes all of 2 seconds. If you are really doing your job, you can ask why the person is missing. Maybe you can have their friend take them some homework. A surveillance system can't do that.
I mean... Why would you ever want an automated system in this circumstance? It just makes no sense.
I think the reality of the situation is that they really wanted a surveillance system. They didn't want to record attendance, they wanted to know where the students were in every second of the day. They wanted to time home long they are in the toilet so that they can catch them smoking or dealing drugs. They wanted to see them leaving the school o that they can lie in wait and nab them as they cut class: students 2 and 5 are supposed to be in band class but they are headed in the opposite direction -- go all you zigs! For great justice!
I just can't imagine any other reason you'd want this. Perhaps I'm wrong. I certainly hope so!
GDPR explicitly prevents this. Data is collected for a purpose and that purpose only. Collecting data for attendance then using it for catching drug dealers is forbidden.
What is probably happening is that this is some sneaky way of introducing facial recognition in schools and something benign like attendance was the excuse. That, however, is a separate conversation from my original post of how would you automate attendance without using facial recognition.