Although, at first blush, you might be inclined to think that the judge in this case got it wrong under the law - after all, New York State's highest court recently held in Trupia v. Lake George Central School District that assumption of the risk, or a child's risky behavior, does not inherently bar a school negligence claim under New York law - a closer reading of the case is required.
In Heatley v. State of New York, the plaintiff was injured while taking part in a "trust exercise" during a First-Year Acting Course at SUNY. According to the plaintiff, the teacher directed these college students to run "with full force" with their eyes closed, and that she sustained personal injuries when she banged into another student.
It's true that assumption of the risk will not act as a bar to personal injury claims as a matter of law. All that means is that the court is not obliged to dismiss the case before it ever reaches a trier of fact. But that doesn't mean that the trier of fact cannot conclude that the school wasn't guilty of negligent supervision, or that the student voluntarily assumed the risk inherent in the activity, and therefore the school isn't liable.
That's the difference between having a case decided on the papers as opposed to at trial.