Saving Grace by Jon McConnell

Middle school English teacher Gabriel Walker always joked that his students were going to kill him; he never thought it might actually happen. After a mysterious epidemic turns children into psychotic killers who rule the night, the world descends into chaos. Gabriel and a small group of survivors are alive because they hide in plain sight; they broke down their own door, busted in their windows and even took pictures off the wall to make it seem as if the house was abandoned in a rush. The survivors have a system of survival and it works. But when they run into Grace, who might be the last healthy girl on earth, everything changes.

The Time Trials by Jon & Dayna McConnell

"Four players. It's in the rules." "Is this like, some sort of academic decathlon or something?" "Something like that." Walkman-toting, guitar-playing Finn Mallory blames himself for his parents' deaths and would do anything to turn back time and set things right. So, when he's recruited into a secret club at his new school that specializes in competitive time travel games, Finn sees a world of opportunity open before him. The games, however, are far from benign. Competition is cutthroat. Scenarios are rigged. And the mysterious timekeepers who organize it all have no qualms about using-or disposing of-players to suit their own sinister plans. Now Finn must decide who he can trust while making peace with his past if he's to have any hope of leading his team to victory and surviving his junior year. As the games commence, it's time to press rewind. “A resonant blend of teen drama and SF adventure." - Kirkus Reviews