Microsoft Surface RT devices does not support External Ethernet so far and there were some workarounds to make it work. But even those solutions are not working right now. According to ZDNet, Microsoft is working on bringing External Ethernet support to Surface RT devices.
Also Microsoft is working with hardware partners to make external Ethernet dongles that support Connected Standby, the Windows 8 feature that provides instant-on/off whenever network connections are available.
Another related news about Surface RT is that Microsoft has extended the discounted Surface RT availability program for qualifying education institutions till end of September.
“In June, we announced a one-time offer for Surface RT that starts at $199 for qualifying education institutions, valid for all K-12 and universities purchasing from Microsoft. Thanks to great customer interest, we are thrilled to share that this special offer to education institutions will continue until the end of September. Microsoft has a long tradition of supporting education institutions, and this offer is intended to get Surface in the hands of even more educators and students.”