Mezrein, you ask:
" For the school ground hunting, if I do it during the summer when schools out, do you think I would still need to contact the principle? "
I don't know why you would need to "ask the principle", to begin with (I mean, I'm assuming you're planning to go when school is not in session). So if the school yard is open to any other after-school usage, then your hobby should be no different (assuming you're not leaving a mess, being a nuisance, etc...). For example: if others go there to jog the track, use the monkey-bars, fly a kite, etc.... then I would assume that the school yard is not buttoned up. In that case, if there is no specific prohibition to your activity, then you would no more need to "contact the principle", than those other people did who use the swings, job the track, fly a kite, etc...
Because to think you need to "ask", merely presumes that there is something inherently wrong, or damaging, about your hobby, that you needed to ask. And with that inference in their mind, you can sometimes get a "no", where ...... in fact ...... no one might ever have cared, or given you a second glance.