Huh... The entire point of a BIOS password is to prevent changes to the device, which includes booting to alternative media. It's an administration thing, meant to stop the computer from being fundamentally altered. Being able to boot to USB makes said password entirely pointless.
Lemme test something before pressing the reply button.
Yeah, I just tested on a Dell and a BIOS password stops me from booting to a USB.
I'm kinda surprised that you'd be able to do so. Dell really dropped the ball with that one - 'cause that's pretty much the entire point of password protecting the BIOS. You set it to boot first to the internal drive and lock it down. We used to do this with nearly every computer at my old company, as well as a case lock.