A Riddle to solve

[Spycam]

3 friends, John, Peter and Mike go to the same school. Every day they
all walk there. John arrives at 8.30 am. Peter 5 mins later than John
and Mike 5 mins later than Peter.

But one morning Peter's mum rings John to say that Peter is not well and needs the day off and would he tell the teacher this.

What time does the friend's teacher arrive at the school?

[Martin]

Is it 8:40 Roy?

[William R]

Any time before 8.30 AM to get the message.
[8D]

[katb]

Is it possible that Mike is the teacher and he arrives at 8:40?

[muffers]

This is a trick question so could it be that Peters Mum is the teacher or could it be that John is the teacher as he arrives first. I'm biting my nails here!!!!

[Lynne]

Do we know that they all had the same teacher!
Iam confused
[]