What I often do on cheap bikes with poor brakes is to swap out the brake pads. I just did that on a Huffy rebuild. The cheap little pads on the Huffy's canti-brake would hardly slow me down, much less stop the bike. I put on some Jagwire Basics pads, and the difference was night and day. The Basics cost me $15, and the kids like that they come in different colors. Kool Stop Salmon pads are another excellent choice, probably even better in stopping power than the Jagwire pads.