Look at it this way, in many cases a school IT guy make be extremely overwhelmed. My high school had like .334 IT people on the staff that was comprised of principals, teachers, and students with some free time. With all of the systems that they had it's amazing that they kept it running at all. In your sending him this email, what you did is you exposed a weakness in his system. When you did that he took it personally and in so doing lashed out at the one person who was trying to help him. it kindof reminds me of what me and my friends did in high school, take advantage of one of the vulnerabilities to send them a message telling them it exists. (we used a loop hole to access a network drive that contained a host of really important stuff, and used some of the novell netware stuff to inform them as such). Obviously the IT guy feels threatened now that he knows that someone has found his holes. I think that's all it boils down to. He was threatened because he, a professional, felt like his short comings had been exposed by someone much younger and less experienced than he. I would take it as a compliment, because it shows that for once you knew about something a professional didn't catch...good job.

At my school the important stuff was also on a different subnet, same network though. funny, like that where I work too.