That's assuming they didn't use computers. Your calculation assumes that the computer uses a full 350+ watts of electricity. If it had a 350 watt PSU and was drawing that full load - it would shutdown (I've had this happen). Even then the CPU doesn't require 350 watts of power [1]. The only device that I know of that will use and designed to use a full load is a bitcoin miner.
Taking in consideration that these computers might have been left on already. I would argue that he used MAYBE an extra 50 watts of electricity [2]. So assuming $0.10/kw/hr (which is the cost of where I live) - he wasted a whopping $0.12/day or ~$50/year.
You have to take into account if the computers were already on. He didn't waste electricity because someone left their computer on - his "waste" would be electricity use that is above that of an "idle computer". It should also be pointed out that if the computer has Mcafee or some other crappy AV the CPU usage would be 100% anyways due to poor programming of the AV software (I have personally seen this many times and you don't know how many times people complain about their slow computer because the AV is using 100% of the CPU).
There is no way he wasted $7m - and even if he did and no one noticed that is part of a larger problem. Besides they only claim he wasted $1.2m - $1.6m [3] - with no evidence of how they came up with that number. That is saying he managed to waste over $100k/year (over 9 years) in equipment purchases, electricity etc - and NO ONE noticed this? I find it hard to believe that the people managing the budget were like "$100k unaccounted for this year? no big deal...". And even if it was accounted for and signed off - there should be 2 people fired - his and the guy who approved the purchase.
Even from the article:
> would find that in a middle of a lesson, the SMART Board had turned off.
This has happened to me personally on my own laptop. Not because I was mining bitcoins or running seti@home. In fact I've seen them installed and they are such POS that no instructor I know actually uses it as a SMART board.
[1] https://en.wikipedia.org/wiki/List_of_CPU_power_dissipation_...
[2] http://i.stack.imgur.com/4HQPY.png
[3] http://www.azcentral.com/news/articles/2009/11/30/20091130se...