The judge denied motions by lawyers for Anissa Weier and Morgan Geyser to have their bails reduced from $500,000.
"The risk of flight is high,” Judge Michael Bohren said. “Parents can do the best they can...but that doesn't always work."
Geyser's lawyer was also unsuccessful in convincing Bohren to release Geyser to the custody of her grandfather, according to ABC affiliate WISN-TV in Milwaukee.
Bohren said, "The court cannot risk what Morgan Geyser is capable of by allowing this bail to be modified."
Her family left court in tears, WISN-TV reported.
Weier and Geyser have been in jail for two years. No date has been given yet for their trial.
Weier and Geyser were arrested on May, 31, 2014, after allegedly stabbing their then-12-year-old friend Payton Leutner 19 times and leaving her in the woods in their hometown of Waukesha, Wisconsin. Leutner was rushed to the hospital with life threatening injuries and survived the attack.
The teens were 12 years old at the time of the alleged crime.
Prosecutors have said that Weier and Geyser were obsessed with the fictional character Slender Man, who is often depicted in fan fiction stories online as a horror figure who stalks children.