I worked with child welfare in my county for 7.5 years. I saw every case of abuse and neglect, read every file and knew the circumstances of each case. I realize that this is anecdotal, however, the overwhelming majority of these cases came to the attention of child welfare through reports of concerned neighbors and families. Now, yes, there were teacher reports as well in some cases, however, I don't recall a case where the ONLY report child welfare received from the school.
My point is that it is a mistake to discount the concern of immediate family and neighbors in favor of the school system.