Advice on Network for Charity

Ok then
I’m about to imbark on the install of a small network comprising as follows
12 X PC’s for training
2 X office PC’s
5 X PC’s for Teen access.
This is for a local charity that wants to provide community training in the like of word andthe internet.
I’ve got 20 IBM desktops , 20 HP Laserjet 4’s , 2 X IBM Servers(330’s)plus an External DLT – these were donated free

The office PC’s should not be accessable from the others and they all require shared DSL access.

any advice ? thanks on advance