What if they ask you not to tell anyone — and it's something you must report?
Honour every request you legally can, and be honest immediately about the one you can't: "I'm going to do everything you asked. One thing I can't do is keep this part secret — the law says I have to involve people whose whole job is protecting you. I'll tell you exactly what happens next, and I'm not going anywhere."
Under Ontario's Child, Youth and Family Services Act, the duty to report is yours personally — you must call a children's aid society directly and cannot delegate it. For 16–17 year olds, reporting is permitted rather than mandatory, which gives you room to plan next steps together.
Source: Ontario College of Teachers, Professional Advisory on the Duty to Report; OACAS.