I have been a nurse since 80's. I have never heard of practising IM injections on fellow students, in those days blood taking was done behind educators back, when free reign in prac room.
I would suggest it is unsafe practise even injecting saline. The university or place of education is at great risk of just this type of thing. Even though a student may/ may not suffer physically, obviously emotionally she has and this is reason for legal action.
Bullying can go on and a student can be put in a poor position to succumb to this, especially if the educator is the one that has suggested this practise.
Even in the old days, oranges or dummies have been used for practise. My first IM on a human was on a patient and I have never had problems or complaints with IMs, nor catheterisation nor iv starts, nor blood taking and they were all practised first on dummies.
I have worked with student nurses, in Victoria, NSW and Queensland and would not have asked them to practise on each other. I ordered a box of oranges. I believe doing anything that is evasive, is not done to fellow students.
I would be surprised if the USA or the UK universities allow this practise.
I could not give IM to a fellow student/colleague for the fun of it, even at my age and experience. Unless they were unwell and I was in a professional capacity.
I would have to say, that this was most unusual practise in Australia.
It is most likely nothing written anywhere, just the legal reasons why it is not practised, and in Australia there is high immunisation rates so most students remember very well what a IM injection feels like.
It is also different 'feel' depending where you give it and to who you give it, fat, thin, old young, indigenous type skins, weathered skin, old skin and 'how' you would give it, size of needs etc etc, it is an assessment before you give the IM injection.
That is why it is 'practised' trying to think of a better word, on humans in clinical practise under mentor supervision after assessment, how best to give the IM injection depending on all the above factors, also with okay from patient, so there is also no point of doing it on other students, it is these reasons why it would be seen as unprofessional.