When Flavia Peréa’s 6-year-old son left the Albert F. Argenziano School in Somerville on Nov. 12, 2019, his behavior chart was marked green, indicating he’d had a great day. That made the disturbing calls she’d received earlier that day all the more perplexing.

The dean of students had phoned her to say a girl told them her son had touched her inappropriately in their first-grade classroom. The dean characterized her son’s alleged conduct as sexual harassment and said the school would have to report it to the state.

She mentioned nothing about notifying the police. But a while later, a Somerville detective left a message on Peréa’s voicemail.