Though York was used in a Braun ThermoScan Ear Thermometer commercial when she was eight months old, her first real acting jobs began at age nine. She auditioned for a talent agency and was approved to be represented, after which she began going out on auditions and getting minor roles. Her first role was in 2003 as an extra in the short film "The Vest". Her first major film role was in 2003 at age 10 when she was given the part of Kim Baker in the box-office hit Cheaper by the Dozen. For their performance York and her cast-mates won the Young Artist Award for "Best Young Ensemble in a Feature Film". In 2004, she filmed The Pacifier. Her portrayal of younger daughter Lulu Plummer was well received. In the summer of 2005, York headed back to Toronto to film Cheaper by the Dozen 2. From 2006 to 2010, York appeared in eleven episodes of the Disney series Hannah Montana. York stopped acting in 2010 after Hannah Montana's fourth season had finished production. She stated she would not return to acting in the future.