I see that you don't know the legal difference between an interrogation and an interview.
Well, gee willikers, I seem to recall from my THREE YEARS IN LAW SCHOOL that for all intents and purposes there isn't a difference worth mentioning in the context of this thread.
However, since you have admitted to not being an attorney in another post, let me give you some free legal advice:
The test as to whether questioning is illegal isn't whether or not someone is being questioned, but whether or not he or she is being questioned WHILE IN CUSTODY and, further, that it is highly unlikely--if not impossible under current US law--that spending a period of time equal to a recessin a principal's office would count as "custody" for the purposes of determining whether or not a questioning/interview/interrogation was illegal.