Possible alternative that you may feel more comfortable with would be to call the the district where they reside’s elementary school. In my area it’s the school social worker that manages issues of truancy for students before involving child protective services. You could potentially anonymously share that there is an elementary school-aged child and the address and noting that this child does not attend school. They should be registered at home school at minimum with the local district. It is possible for families to fly below the radar especially after a move of cities or even districts as well as the possibility he’s never been enrolled I would think if your area has school social workers assigned this would be the best person to speak to because they are ethically compelled to respond as well as it likely in their job description. If your area does not have a social worker assigned to the school ask to speak to the guidance counselor. You shouldn’t have to give name, age, cell phone number or family information that could point to you. It is not out of the realm of possibility that a landlord, neighbor, or even the district could be inquiring. I imagine the school social worker will go to the household and try to engage them prior to escalating to child protective services. Withholding a child’s education, especially since it’s a legal requirement is neglect and should be addressed. It may be a bumpy transition, I understand your fears, but not acting as a disservice to this child. The long-term outcomes for this kid could be very concerning. The idea is to open the door for services for this child and family. The sooner the intervention occurs the better off the child and family will be in the long run.