BARTOW, Fla. — Students across the country are heading back to school this month, amid a growing crisis to hire and keep qualified teachers. At the start of the last school year, more than 100,000 classrooms were staffed by teachers not fully qualified to teach, equivalent to about one classroom for every public school in the U.S.

Nationally, about 20 to 30 percent of new teachers leave the profession within their first five years. As CBS News correspondent David Begnaud reports, schools in Polk County, Florida, are scrambling to fill vacancies.

The superintendent for Polk County, Jacqueline Byrd, needs every qualified teacher she can get to manage her massive 104,000 student school district. But they'll be short at least 100 teachers when students return to class Monday.

"You look at our generations now, younger generations. They're choosing other areas to go into besides education," Byrd said.

Around the country, the number of vacancies is staggering. Between 2009 and 2014, teacher education enrollments dropped 35 percent.

Teacher enrollment has gone down over the years. CBS News

"We've been watching it, but we can't no longer sit on the sidelines and just watch it. We've got to begin trying something," Byrd said.

She is taking a new and unconventional approach. Just two years ago, she began working with Polk State College and the school's president, Angela Falconetti, to create a teaching academy. The program allows sophomores in high school to take teacher education classes which count toward their high school and college degree. By the time they graduate, they'll have their associates degree, and a full teaching degree two years later.

"It's a quality, quality education that we offer and we prepare them together as they will have many internship opportunities and field experience in the public school system. Direct employment with the public school system," Falconetti said.

Polk County, Florida, is trying a new program to try and encourage more students to become educators. CBS News

"We are scrambling to try to find teachers," said Marianne Capoziello, president of the Polk Education Association.

"It's gotten bad... this is day three of the teacher year and I've already had two teachers resign," she said.

Capoziello says teacher pay is one of the biggest factors. The estimated national average teacher salary last year was $60,483. In Polk County it was just over $41,000.

"It's not competitive enough to attract people," Capoziello said. "Not only do we have to get them here, but then we have to work to retain them in their classrooms so that we don't have this constant every year churn."

Capoziello also said she blames scheduling, saying teachers often work 12 to 14 hour days, seven days a week and that the low salary doesn't go far enough. But, she says often times teachers just want respect in their profession and to not be taken for granted.