Nicole Powell works with students who have a range of talents, from gifted to learning disabled

There are 3.5 million teachers on the job in public school classrooms across the United States. It's the country's largest professional workforce. Teachers are trained in colleges or work in other fields and get their teaching credentials after some additional schooling. While there are plenty of teachers certified to teach, the problem facing American education is keeping new teachers like Nicole Powell in the classroom.

On this day Powell hands out a study sheet to help her middle school students review for a mandated state science exam. It is Powell's first-year at North Bethesda Middle School outside of Washington, and she has five large classes with 32 students each.

Nicole Powell makes times for individual students during class

Maryland, like most U.S. states, requires that all public school teachers have a college degree, a mastery of their subject and supervised practice-teaching experience. Many students complete these requirements in four years. Powell went on for a Masters degree in education. "I went to school at night and student-taught throughout the entire day." Powell says she spent more time practice teaching than her peers with four-year degrees. "I felt like I had more experience going through my graduate program than I would have as an undergraduate."

During the year-long program, Powell was assigned to a school, observed many classes and worked alongside a mentor. "I started off modeling, following her lesson plans, mimicking what she did, but at the same time it was me doing it. And then I began planning my lessons on my own, and then it was all me."

Dan Gabel helps Nicole Powell fine-tune her teaching techniques

Powell's education did not end with graduation. All new teachers in the Montgomery County, Maryland, Public School System are required to work with a consulting teacher who makes regular, unscheduled classroom visits.

Dan Gabel, a 25-year veteran science teacher, works with Nicole Powell. He comes to class with a notepad and a computer to record everything that happens and discusses it with Powell afterwards. Powell says the frequent contact has made a difference. "I can handle kids misbehaving. And the longer I am teaching, the better I am able to get kids to stay on task, the better I am capable of stopping problems before they start."

Consulting teacher Dan Gabel makes regular visits to Nicole Powell's science classes and records what he sees

Powell says, while she is learning a lot on the job, her education didn't prepare her for the realities of the classroom. She has students who speak English as a second language, very gifted students and students diagnosed with learning disabilities.

She says she never had a course in college about children with special needs, which she says would really have helped. "I am thrown into this environment where I am expected to accommodate up to 15 kids per class who have these accommodations and I have never dealt with special education before."

The job isn't easy. Half of all teachers quit within five years of their first assignment, according to the National Education Association. Segun Eubanks, who directs the association's teacher quality program, says NEA surveys cite poor working conditions, low pay and lack of resources as major factors in this exodus of teachers.

He fears teaching will become a revolving-door profession unless colleges and school systems step up to support life-long learning. "So it is about building a continuum of professional growth, and we are challenged to implement that in real and meaningful ways."

Middle school students take class time to study for a mandated science exam

Nicole Powell says she has gotten the resources she needs so far. Maybe that's why she says she expects to be on the job in five years. "I love teaching middle school science."

Powell says the public school system in Montgomery County — one of the most affluent counties in America — offers many attractive job benefits to encourage her to stick around. Benefits include help with tuition costs should she someday want to go back to school to become a principal.