Fact: RFIDs have a range in the 10s of feet. So the school can't monitor you off school grounds. The SROs obviously detected several students leaving the building and followed them. No homing beacons needed.
Fact: most major corporations use some method of access control. How many people need to show IDs, badges, or scan their way into work? So what is the big deal if the school can see that a student is in the back hallway (or better yet, two students... since a nearby school has had multiple incidences of students caught in stairwells, maintenance halls, etc. having sex already this year. And for every couple you catch...) when they aren't supposed to be? Schools already have hall passes for access control; why shouldn't they make the system better?
Fact: students do not have the "right" to wander where they please. When a teacher says "Go to the bathroom," it's not a license to wander the halls. And if an RFID tag shows that a kid is wandering, then it is doing him a favor (by teaching him accountability). All of the parents who are hyperventilating over this are the same parents who are making our schools uncontrollable in classes ("You don't have to do what the teacher says"... but wait until they try to kick the defiant brat out: "My son has a right to an education!").
Sorry, but unless you can show me where the school is tracking kids at home or at the local mall, this is a non-event. A school is well within its prerogatives in tracking its students on campus.
RFID read distance record is 217 feet
This kind of thing is improving constantly.