SALZGITTER, Germany—Late this summer, Nadine Langer took her six-year old to her first day at school. The girl was one of two German children in her class, she said, amid 20, mostly Syrian, refugees.

“I am not against foreigners,” said Ms. Langer, 41. “But there is a point where we have to wonder who is integrating whom.”

Germany’s 2015 refugee crisis has largely disappeared from the headlines. But in this and other midsize towns, it is continuing to unfold, putting communities under stress, pressuring local coffers and feeding concerns about safety, jobs and the quality of education.

Some 140,000 asylum seekers have entered Germany so far this year—a sharp drop from the 1.2 million who arrived in the past two years. But in places such as Salzgitter there is a sense that the government, having housed and fed the newcomers, is failing in the longer-term effort to integrate them in German society.

This unease, pollsters say, boosted the anti-immigration Alternative for Germany at last month’s election, making it the first far-right party to enter parliament in half a century. This shock means immigration will loom large when Chancellor Angela Merkel kicks off negotiations on Wednesday to form a three-party ruling coalition.