Alyssa Shepherd, 24, was found guilty of three felony counts of reckless homicide, a count of criminal recklessness and passing a school bus causing injury.
She faces more than 20 years in prison. Sentencing is set for December 18.
Alivia Stahl, 9, and her 6-year-old twin brothers Xzavier and Mason Ingle were hit and killed as they were getting on their school bus in October 2018. A fourth child was also injured.
The family of the three victims pushed hard for a bill that increases penalties for a driver who disregard flashing red lights and stop arms on school buses. It became state law on July 1.
Residents can now face up to a year in jail and up to a $5,000 fine for passing a school bus with a stop arm out.