What you're describing is the American school system. As a Swede who spent an exchange year in an affluent Dallas suburb the systems couldn't be more different.
Going from Swedish to American high school felt like stepping back to elementary school in regards to personal freedom and trust.
First to set the base, in general in Sweden you have all your classes with the same 25-30 instead of different groups every period. From 7th grade we had our own schedule complete with periods without lessons where we would just hang out, walk around or go to the library and jump on the computer. In high school this ramped up even more. Loitering as a concept doesn't exist in Sweden.
To accommodate this the design of schools are completely different. The endless hallways don't really exist, instead there are areas between the classrooms with sofas, tables and whatever to enable people to hangout or study together. My school even had a café open all day. Doing group projects is the epitome of this, we'd show up at the start of the class for attendance and then take off to the library or some other place.
Contrast this with America. Hall passes to go to the restroom, hall monitors. We even had CCTV surveillance in the entire school building. If you would show up late you could be sent to the cafeteria and forcibly miss the class and have to write some essay about how wrong you were. How can a person learn to take care of themselves in such an environment?
This isn't even talking about the pledge or national anthem over the PA system.
Sorry for the rant.
Back to the topic on hand, from what I've read on Swedish news about it everyone involved generally was positive. No more the annoying wait while taking attendance. For the parents it was no different, even before this system they still immediately got a text if the kid didn't show up for class.
The questions raised by the DPA are relevant and my guess is that this will continue to be explored but with more caution towards how the data is processed to comply with this ruling.