TALENT, Ore. — It was the first day of school, and the fifth-grade teacher invited her students, seated in a circle on the floor, to swap summer stories in English or Spanish. One described a family trip to Spain. Another recounted a fun day at the movies. When it was his turn, José Miranda Taracena took a pass.

The 11-year-old Guatemalan boy with ink-black eyes and a coy smile had spent most of his summer in a foster home in New York with his 7-year-old sister, Mayda, after immigration authorities arrested their mother near the Mexican border for entering the United States without authorization.

Now the family was back together, but he was not ready to tell his new American classmates about a summer dominated by those 51 days.

José, Mayda and their mother, Lillian Taracena, are trying to make a fresh start in this small town in southern Oregon. The siblings started classes last week at Talent Elementary School. Ms. Taracena spends her days getting settled into the small trailer they’re now sharing with her cousin, making the required check-ins with Immigration and Customs Enforcement and consultations with lawyers.