Across the nation, alternative-route program officials say they are seeing increasing enrollments from career-changers with strong backgrounds in the highly sought-after fields of math, science, and technology. But the extent to which school district administrators are primed to take advantage of larger--and in some cases stronger--talent pools in those fields depends on the officials' ability to negotiate the factors affecting the teacher labor market, say experts familiar with hiring practices. Despite state efforts to create pathways to teaching tailored to math and science professionals, the downturn has shrunk the overall availability of teaching jobs. That means not all people with strong credentials in those fields who turn to teaching will have positions waiting for them. The recession has made it more difficult for once sought-after math and science professionals to land a teaching job. Theoretically, an influx of professionals with science, technology, engineering, or math--STEM--backgrounds is a boon for districts, which have historically struggled to attract enough math and science teachers.