Hi,
First of all, the global situation : I play ACNL with the Welcome Amiibo update. I use Soundhax for hacking and I've done it since january now and didn't seem to have any problem (I've always followed all the steps and never done the dangerous things mentioned in the Save Editor site help...
One of the sites that weren't blocked on the school's network was some file uploading sites. I would upload some games, write down the URL and take it to school one day.
my school has a chrome extension called light speed filter agent and it legit blocks YouTube pfps since the file cdn(I think aka yt3.ggpht.com) is classed as mature
It was easy to bypass some of the restrictions, as one of the admins left a registry key in the administrative shares drive, which allowed me to get around the blocking of some sites.