BALTIMORE – The Baltimore Sun reports that “more than 700 Baltimore County teachers” are leaving their posts this year, making it “the only school system in the Baltimore area that is reporting a substantial rise in the number of teachers leaving.”

700 teachers are either resigning or retiring. The big difference is the number of resignations.

Two years ago 325 teachers resigned in Baltimore County, and that total has risen to 418 this year. Annual retirements have remained around 300 per year.

MORE NEWS: Know These Before Moving From Cyprus To The UK

According to the Sun, part of the reason for the spike in resignations is Baltimore County’s adoption of Common Core standards.

“Teachers around the state faced an array of changes this year, including new teacher evaluations and a new curriculum to match the Common Core standards,” the newspaper reported. “In Baltimore County, the flawed rollout of the new curriculum upset elementary school teachers, who filed a grievance.”

The Maryland State Education Association has had more complaints about the Common Core implementation from teachers in Baltimore County than from elsewhere around the state, the news report said.

“People in Baltimore County have been very vocal about that lack of support … so much changing at one time,” said Cheryl Bost, vice president of the union.

Graham Long, a 29-year old social studies teacher at Catonsville High, said he’s quitting due to “workload fatigue”

“Collecting all the student data and doing all that analysis has put a burden on the teachers,” he said.