The above statements were accurate.
Please check the photos at www.bmxtrix.com
-> how-to -> fix your bike -> bike basics.
It shows the front brake cable being routed down through a hole in the stem, down the forks, and then it loops back up into the front brakes from underneath.
If the bike you bought has this hole but brakes were not setup this way and the models at the store that you bought the bike from ARE setup correctly, then return the bike.
It is always recommended that you (at the very least) buy a bike from a bike shop instead of a toy store. While bikes are fun, they are also your childs main form of transportation and need the same reliability as your car does. Would you buy your car from a department store if you knew a minimum wage employee put it together? Just some thought. Bikes from toy stores can be marginally okay, but should be checked by a mechanic for proper setup.