The use of network proxies is not supported by ReplicatorG. ReplicatorG has been abandon-ware since Nov 2012. A version is only provided as one means of uploading .hex files to a MakerBot printer.
You could install ReplicatorG at your home, allow it to connect and collect files, then zip the directory ~/.replicatorg into a zip file, put it on a thumb drive, then unpack it on the target system at school into ~/.replicatorg. You'd then be good to go.