It started as schoolyard roughhousing during recess, with one boy’s hand allegedly touching the upper thigh, or perhaps the groin, of another. There were no reported witnesses, and it remains unclear if anyone complained, but the principal immediately suspended the student, placing the incident on the boy’s record as a case of “sexual assault.” The children involved were first graders — the purported assailant just 6.

“It’s really overzealous,” Levina Subrata, the accused boy’s mother (they do not share the same last name), said of the incident last month at Lupine Hills Elementary, a public school in Hercules. “They were playing tag. There’s no intent to do any sort of sexual assault.”

The school’s principal, Cynthia Taylor, did not respond to an interview request. Marin Trujillo, a spokesman for the West Contra Costa Unified School District, which includes Hercules, said officials were barred from speaking about student and personnel matters. However, he added, “We must take any allegation of assault involving a child very seriously.”

Ms. Subrata provided a copy of the suspension notice, which shows what appears to be the principal’s signature and the conclusion: “Committed or attempted to commit a sexual assault or sexual battery.”