On impact, Holden's helmet flew off and he was thrown through the air, sliding under the truck, where his skull hit the vehicle's axle.
"It was the worst call," Ricky, 38, recalls about the sobbing message he received over the phone from his son's best friend.
When they arrived at the hospital, the parents saw that Holden's condition was much worse than they thought.
"He was bleeding out of his head and his ear," Andrea says. "He was shaking from the shock, and he was in pain. That was the worst for me, seeing my son suffering."
Lengthy RecoveryAfter two surgeries and nearly a year of recuperation, Holden – now 16 – pulled through. Adjusting back to life as a teenager, Holden is happy and healthy, entering his high-school junior year and preparing for his SATs.
But through this experience, the Schroders are more thankful for their blessings.
"There's nothing harder that we've been through," Andrea admits, saying she and Ricky are now more cautious when it comes to their kids because, "You see how fragile life is."
For more on the Schroder family – including life on their 30-acre Calif., ranch and Andrea's shot at TV reality stardom (she's a contestant on Bravo's Top Design) – pick up the latest PEOPLE, on newsstands Friday