The school wouldn't be able to tell the parents however, from my experience the school system doesn't know how the assessment works at that age.
Also are you saying they are starting the diagnosis testing as the area where I'm from it takes around 5 years so if they are only just starting the process then I wouldn't expect to receive a diagnosis whilst still at college
So I got mine done when I was 16 (an adult assessment)
So I got some forms with around 20 questions on and had to answer them and send the form back. At this point it was only me that needed to answer the questions.
However, when I went to the assessment they said to bring someone along who has known me since childhood to answer the questions
I then had to do a couple of tasks (nothing too scary also can't give details) but just simple tasks like a puzzle or tell a story, describe your family, how would you do this sort of thing
Then my mum went into a different room and we both answered around 50 questions mini interview style and then we came back together and asked a couple more questions
Feel freee to ask anymore questions that you might have