Once again, adults entrusted with the care of children have let them down.

If you've been following the news lately, you've no doubt been horrified by accounts of a Los Angeles elementary school teacher who allegedly subjected students to lewd acts, and revelations that complaints by students and parents had fallen on deaf ears for two decades.

The teacher in question has been accused of blindfolding and gagging students, and feeding them his semen. He was arrested late last month after a long investigation spurred by a drug store clerk who noticed disturbing photos that the teacher had dropped off for processing.

But as shocking as the details emerging in this case have been, they are also heartbreakingly mundane. Time and again, we bear witness to the victimization of the most vulnerable and innocent among us, and the callous behavior of those who are complicit in the abuse because they chose to look away.

I've written about child sexual abuse before, most recently in this column not long after the Penn State scandal broke. I've covered the stories of abuse survivors such as Newport Beach residents Joelle Casteix and Elaina Kroll, who have channeled their pain into lifelong quests to hold pedophiles and those who shield them accountable.

In all the accounts of child abuse that I've come across there is one common, recurring thread: the unheeded cries for help that result in victimization twice over.

Make no mistake: those who have any reason to suspect that a child is being harmed and do nothing are guilty. In a collective sense, we are all culpable.

Truth be told, were any of us really surprised to learn that complaints had been made for years about the accused, Mark Berndt, who taught at Miramonte Elementary School in south Los Angeles?

One former student, for example, has come forward with allegations that during the 1990-91 school year a counselor told her and two other girls to stop inventing stories after they complained that Berndt appeared to be masturbating behind his desk. Other complaints by students and parents also led nowhere.

Now a second teacher at the school, Martin Bernard Springer, has been arrested and charged for allegedly fondling a child. Last week, in an attempt to quell parents' concerns, school officials temporarily replaced the entire Miramonte staff, though that's likely cold comfort to those whose voices have been ignored for so long.

The Miramonte case is only the latest example of authorities failing to act on evidence that something was amiss. Such lack of diligence happens in virtually every community, and for a variety of reasons — laziness, prejudice, insularity, cronyism and willful ignorance come to mind — yet the effect is the same. Kids that have been mistreated in the most horrific way are subjected to yet more trauma when their pleas for protection aren't taken seriously.

I sat through a Newport-Mesa school board meeting last month, and as the hour grew late, the crowd thinned out. The news of former Supt. Jeffrey Hubbard's conviction and subsequent firing had been dispensed with, and other district business had concluded.

There were few people left in the audience, but I couldn't help noticing a woman seated near me who had stuck it out. She looked familiar, yet I couldn't quite place her.

When the time came for public comments, she approached the podium. She identified herself as Karyl Ketchum, the mother of Hail Wiggins-Ketchum, who graduated from Corona del Mar High School in 2009.

Then I remembered. Hail was the young woman at the center of a disturbing incident involving a group of CdM football players who posted a Facebook video in which they discussed raping and killing her.

At the time, Hail and her parents sought help from CdM and district officials, and other authorities, but said they received little or no response. They went public with their complaints that too little had been done to protect Hail and punish the athletes. The American Civil Liberties Union filed a lawsuit against the district that ended in a settlement calling for students and staff to receive anti-harassment training.

Karyl Ketchum looked straight at the board members and accused some of them of a pattern of shielding bad behavior. Their steadfast defense of Hubbard during his trial — and in spite of sexually suggestive e-mails he sent from his work account — was only the latest example, she charged.

Many of the board members had a deer-in-the-headlights look on their faces, and when Karyl Ketchum concluded her impassioned speech there was an awkward moment of silence. What was going through their minds? Was there any regret, or silent acknowledgment that things could have been done differently?

How would I feel if it were my child? Surely I'd be filled with same kind of righteous fury displayed by Ketchum and by the parents of Miramonte students. Ketchum later told me that every time she learns of another incidence of a student being mistreated, she relives the emotional torment of her daughter's ordeal.

The least we should expect of those entrusted with our children is that they'll do everything in their power to protect those kids from harm, and that they'll be listening — really listening — to pleas for help. Any less is akin to helping abusers hide in the shadows where they can continue their heinous deeds with impunity.

PATRICE APODACA is a Newport-Mesa public school parent and former Los Angeles Times staff writer. She is also a regular contributor to Orange Coast magazine. She lives in Newport Beach.