Watching with interest to what you end up doing 

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I’m not an expert by any means but if you start them indoors with electric heat it seems to me they may have a harder transition to outdoors with no electricity. For more experiences chicken keepers: would it be better to start inside with the wool hen (stable temp environment, probably around 68F in a school) if you were going to transfer to no heat outside at 2 wk, where the high temps are similar but it will be cooler at night?
#1 I would get a small solar/battery setup with an inverter to plug a heating pad into. Most heating pads are under 50watts. That I think is your best option or shortly after you receive the chicks I think you'll be back saying you lost them.
#2 Maybe your " wants" of doing this project is really not feasible seeing how you don't really have the means of doing it. Not trying to be rude just keeping it real.
Good luck which ever way you go.
That was not the janitors closet?The principal and I agreed on an indoor location with a temp of about 74 degrees Fahrenheit.