Youtube Videos are Bandwidth eaters for Limited bandwidth Internet users. Education Institutions also need to block Youtube videos. Here a simple trick for blocking youtube videos using squid Proxy.
Add the following line to /etc/squid/squid.conf
## The videos come from several domains so block all
acl blk_youtube dstdomain .youtube.com .googlevideo.com .ytimg.com
http_access deny blk_youtube