A bizarre vaccine/test done secretly what it is it?!

A bizarre vaccine/test done secretly what it is it?

My sister lives abroad. She is 14 years old. Recently she told me a bizar re story .she said that they get all of their vaccines at school (so far sounds ok ) but the last vaccine/test was somewhat wired. A nurse came to the classrooms injected something to each student arm. they were told that some of the kids will develop a red spot in the injection area. And the nurse will came back in a week to check them again. My sister had developed a red spot on her arm. When the nurse came back she measured each student’s spot (some of them didn’t have any spot at all . the teacher and nurse told the kids with the bigger spot to go see a doctor. my sister was told that it was a borderline spot. So she didn’t have to see a doctor. Nobody knew what was this about? Why the other kids had to go see a doctor ? My sister asked her teacher But she was not answered. Since my sister had developed the red spot after the injection I would like her so see a doctor too? But she think that the all thing is just funny. Does anybody has a clue what kind of a test was it ? (Based on the description above) why the nurse and the teacher had to keep it so secretly? Why wouldn’t they tell the student what kind of test was it? (They just say that it is a normal thing all kids age 13-14 yrs old do )
.I’ m confuse

4 weeks ago
Well, she lives with my mother. In the beginning of the year mothers signed on some statement allowing school do all the medical staff. (They don’t go to a doctor to get vaccines etc. The school nurse is the one in charge on that staff.)
I told my mother to inquire about the test. She said she trusts the school. And any way my sister came out ok. I don’t agree with her. But s she doesn’t have the same opinion as me. Plus I don’t have any right to get my sister privet information. I feel stuck. I just want to know why they won’t tell the kids what kind of test was it. And why it is so important to keep it secretly. Especially when my sister was told that all the schools and all kids age 13-14 have to do that test.

I honestly would contact the school and find ot what this is about the other answer sounds correct, but if the parents did not get a form or info on it along with a permission slip to authorize it I would have to say it could be some what illegal. You are doing the right thing by being concerned and just make sure you or your parents contact the school to find out what is going on.