At my school you were provisioned as <two-digit-start><first-three-firstname><first-three-last-name>. e.g. Joe Bloggs starting in 2000 is 00joeblo

Cue problems when two "Simon Smith" join in the same year. They were given 00simsmi and 00smisim I think.

I am pretty sure they spent 7 years at school forwarding each other email as various teachers assumed the default would work.