(CNN) In California's Robla School District, the littlest of the 2,000 students are in pre-K, then there are the kindergartners up to sixth graders. On any given day, up to 200 of them are missing from the school's virtual lessons.
First, the teachers reach out, calling and sending messages. Then school principals try to make contact -- calling again, sometimes seeing if there is a brother or sister in a different class to let them know what's going on.
And if all that fails to reach the children and their parents, teams of social workers take up the case, to see what can be done to get students back to class, even virtually, amid the coronavirus pandemic.
"We have some families that are having a difficult time with life in general right now," Elisa Olmo told CNN recently as she set out to try to find missing students in Robla, a district in Sacramento, California.
"They're losing their jobs, they're maybe losing their house. And so school gets put on the back burner."
Robla School District Superintendent Ruben Reyes said he was very concerned about the 10% of students who were regularly missing class. The district has done what it can to get devices and Wi-Fi access to families who need them and is now focused on its "student find" program to make sure children are making it to school. He said 20% of his students have no permanent home and 90% live under the federal poverty limit.
"Very often ... we need to physically go out to the home that we have on record, the address, and see if we can reach the family in that way," he said.
"There've been some very interesting stories. Families who were just gone -- the instability of poverty is a big part of this -- so they were there, and now they're not."
Other times, it's an easier remedy like a lost computer cord that can be replaced. And sometimes children have been found left unsupervised and referrals may need to be made to social service agencies.
"It's not about getting anybody in trouble or catching anybody doing anything bad," Reyes stressed. "It's really about really trying to provide whatever that family needs to help their child to be successful."
School districts across the US are seeing plummets in the numbers of children enrolled for classes in the pandemic.
Chicago Public Schools have nearly 15,000 fewer students than this time last year, and Dallas was short of more than 13,000 students, CNN affiliate KTVT reported. It's a similar story across the country as many schools offer virtual-only instruction. Large drops have been seen in pre-K enrollment, Chicago, Dallas and others say, but they do not account for nearly all the missing students.
When students do enroll, schools still see absences and declines in online participation from middle and upper-class areas, where families may have opted for group pods, homeschooling or moving children to private schools. But challenges are magnified in lower-income districts like Robla.
The concern among educators like Robla's superintendent is not just for the immediate, but for the future. Studies show chronic absenteeism can lead to third graders unable to master reading and ninth graders dropping out of school altogether, according to Attendance Works, a non-profit advocacy and research group.
Laurie Butler-Echandia, who was out looking for missing students in Sacramento with Olmo, said the most challenging days were when she seemed to get nowhere.
"It's when the families aren't there. That's the hardest, which happens quite a bit," she said.
This day, she and Olmo did connect with a single father and walked him through how to help get his 11-year-old daughter online.
Outcomes like that buoy Superintendent Reyes: "Those are the heartening stories that I hear from my staff -- we visited this family, and now this child is coming to school."
And with that student back online, the team moves on. "We cannot let even one child slip through the cracks," Reyes said. "That's a lofty thing to say, but that has to be our goal."