The RFID tags are used for attendance tracking and other various tasks. ALL of the schools in the Bexar county area have students who have to wear ID tags on their shirts. The gang problems here are pretty high, they don't want people that look like students to just walk in and start problems. True, it wont stop a student from just handing an id card to another person to walk around in, but the teacher will record the student as absent and the office will see where the student is if they are in school.
Checkpoints aren't near the bathrooms, but they are in the halways and the last time I heard, they were in the rooms as well.
This is also a test by only these two schools. If it passes, they will use them in the entire county, otherwise they will abandon the project all together.
I don't necessarily believe that she should be using the "Mark of the Beast" excuse. But this does cut REALLY close to invasion of privacy.