RALEIGH — The rate of North Carolina teachers leaving their jobs increased slightly last year to nearly one out of eight working in the classroom.

An annual report received by the N.C. State Board of Education on Thursday shows that nearly 12,000 of the nearly 100,,000 teachers employed in the state's school systems left last year. The 12 percent turnover rate is up slightly from 11 percent the previous school year.

Retirement was the biggest reason for turnover. Less than 1 percent said they were leaving because of dissatisfaction.

Eighty percent of the state's 115 school districts said they've had trouble finding instructors licensed to teach high school mathematics, while about two-thirds of the state's local schools reported having trouble finding high school science and special education teachers.