This test was carried out by a gang of girls waiting just inside the classroom by the door. The leading girl has a ruler. All males entering will find a ruler being poked into genital area. Then, depending on your posture, they would should “TIGHT” (if you curled up protectively or seemed shy), or “LOOSE” (if you strode through manfully).
Why? The only explanation I can think of would be that striding in manfully implies that you have nothing to be ashamed of – ie a large penis – therefore you would be requiring a loose vagina. In this sense, it’s not a form of feminine intimidation, it’s simply a pragmatic allocation of available vaginas.