The 43-year-old driver, whose name was not released, was driving middle school children back to school after a zoo visit on June 16 when the president and Republican Rep. Dave Reichert drove slowly by in a motorcade.
From the bus, the children waved; with the windows down in their car, Bush and Reichert waved back.
That's when the driver gave the president the finger, according to Reichert and Issaquah superintendent Janet Barry.
"The congressman hadn't seen it, but the president turned to him and said, 'That one's not a fan,'" said Reichert spokeswoman Kimberly Cadena.
Reichert later called Barry to tell her about the incident, but the bus driver had already been fired. District officials learned about the incident after the driver boasted to colleagues about it, Cadena said.
District spokeswoman Sara Niegowski said the driver has filed a wrongful termination grievance through the American Federation of State, County and Municipal Employees. The union did not return calls seeking comment.
Niegowski said the firing was not politically motivated.
"The bus driver was not terminated for making an obscene gesture at the president. The bus driver was terminated for making an obscene gesture in view of the students," Niegowski said. "That's not the role modeling we need for our students."