Mike Trodd, at Cecil Road Primary school, has written an easy to use guide on how to download YouTube videos using Realplayer.
Videos need to be downloaded at home because YouTube is blocked at school. They can then be put onto pen drives and either re-imported into RealPlayer back in school or, since the saved video stays as Flash video, can be inserted straight into SMART Notebook (version 9.5 or later) or ActivePrimary.
http://www.kented.org.uk/ngfl/ict/multimedia/RealPlayerDownloadInstructions.pdf