Have found it Bomber, thank you.
Nevertheless the game should really let you try the key at the Boy's gate too.

Now, as every quest apart from the escape quest is done, i try hunting down the secret area... any hints ? (if too specific for the board, plz email them.)

> > Hi all,
> >
> > i got a key from the office.
> > When i examine the boy's gate, i get the following text:
> > The gate consists of a set of large steel double doors. There's a little keyhole on one of the doors. Right now the gate is securely shut and locked.
> >
> > But when i klick on the key i get NO Option to use the key on the gate
> >
> > So either the gate description is wrong or you should be able to try the key here ...
> >
> > Btw: the graffiti is no longer on the wall here ...
> >
> > Can i still access the special area ?
> >
> > Inventory:
> > Beaker
> > Coin
> > Hot-Wiring Instructions
> > Mirror
> > Smock
> >
> > Blue Paint
> > Disk with Virus
> > Juice
> > Rust Eater
> > Soldering Iron
> >
> > Bottle Cap
> > Earthworm Sample
> > Key
> > Shirt
> > Wire
> >
> > Chain
> > Eraser
> > Knock-Out Drops
> > Shoes
> > Wrench
> >
> > Chalk
> > Glue Stick
> > Lighter
> > Slip of Paper
> >
>
> There's another place where you can use the key...
>
> --The Bomber who blew a fuse