But educators say that during the recession and its aftermath prospective teachers became wary of accumulating debt or training for jobs that might not exist. As the economy has recovered, college graduates have more employment options with better pay and a more glamorous image, like in a rebounding technology sector.

In California, the number of people entering teacher preparation programs dropped by more than 55 percent from 2008 to 2012, according to the California Commission on Teacher Credentialing. Nationally, the drop was 30 percent from 2010 to 2014, according to federal data. Alternative programs like Teach for America, which will place about 4,000 teachers in schools across the country this fall, have also experienced recruitment problems.

And that has led districts here — and elsewhere — to people like Jenny Cavins.

Ms. Cavins, 31, who once worked as a paralegal and a nanny, began a credentialing program at Sonoma State University here in Rohnert Park less than a year ago. She still has a semester to finish before she graduates. But later this month she will begin teaching third grade — in both English and Spanish — at Flowery Elementary School in Sonoma. Ms. Cavins said she would lean on mentors at her new school as well as her professors. “You are not on that island all alone,” she said.

Esmeralda Sanchez Moseley, the principal at Flowery, said she could not find a fully credentialed — let alone experienced — teacher to fill the opening. “The applicant pool was next to nothing,” she said. “It’s crazy. Six years ago, this would not have happened, but now that is the landscape we are in.”

Before taking over a classroom solo in California, a candidate typically must complete a post-baccalaureate credentialing program, including stints as a supervised student teacher. But in 2013-14, the last year for which figures are available, nearly a quarter of all new teaching credentials issued in California were for internships that allowed candidates to work full time as teachers while simultaneously enrolling in training courses at night or on weekends.