Absent a special duty to the individual, such as (but limited to?) those in custody, right?
Given that there are IIRC at least 19 SCOTUS cases where they've said the cops generally don't have a duty to do anything, I am guessing this decision will stand and the cases will go nowhere (there is another lawsuit against Peterson where the trial judge has rejected his immunity and "no duty" arguments so far).
But public school kids are not Joe Schmoe walking down the street. There's a whole regime of public laws requiring those kids to be in a school someplace, public, private, or in some states home-school, enforced with government money and agents. Seems like the duty to protect them should be at least as strong for them as incarcerated Joe Felon.
...and the duty is owed to all of the kids, not any specific kid.