Students injured while playing sports cannot sue their coaches unless the instructors are so reckless that their conduct was outside the range of ordinary coaching, the California Supreme Court ruled Thursday.

By setting such a high standard, the court provides formidable legal protection to those who coach school sports, weekend soccer clinics or Little League baseball. The ruling also extends to those who teach rock climbing or any other recreational activity.

Yet in the case before them, the justices ruled that a San Jose high school swimmer who broke her neck while diving into a pool could sue her coach. The court said there was a genuine question of whether the coach was reckless in assuring the 14-year-old freshman that she wouldn't have to dive in a meet, failing to teach her how to dive and then threatening to remove her from a meet minutes before the competition unless she dived.

So although the ruling was a victory for plaintiff Olivia Kahn, now 22, the decision makes it tough to sue coaches.

"It's good news," said Fred Gregory, head of the legal commission for the American Youth Soccer Organization. "People need to understand that they can't deal with kids in a way that pushes them into ultra-hazardous situations, (but) as long as you don't, you're protected."

In setting the standard for lawsuits, the justices followed their own 1992 ruling that those who ski or take part in a game of touch football or other recreational activity assume the risks -- and injuries -- that are inherent in the sport.

In Thursday's majority opinion, Chief Justice Ronald George wrote that a coach's liability for player injuries must be limited be coaches must challenge their students -- even if they are negligent in their instruction or supervision -- making the learning process risky at times.

To hold a coach liable for challenging students to go to the next level "would have a chilling effect on the enterprise of teaching and learning skills that are necessary to the sport," George said.

The court concluded that coaches or athletic instructors can be sued only if they intentionally harm a student or are so reckless that their conduct somehow increases the expected risks of a sport.

But Sharon Arkin, a Newport Beach attorney who filed a brief on behalf of the Consumer Attorneys of California, called the ruling "a frightening result for the children of California."

"Now, teachers and instructors and coaches can act unreasonably, and they're immune from liability," she said.

Two of the justices -- Kathryn Mickle Werdegar and Joyce Kennard -- favored a lower standard of negligence, saying that coaches had an obligation to see to the safety of their students. But all seven justices agreed that Kahn, who broke her neck in 1994, could sue her coach and the school for recklessness.

The court said that Kahn had told her coach at Mount Pleasant High School about her intense fear of diving and had been assured by him that she wouldn't have to dive, and he never gave her any diving instruction.

Nonetheless, she said that her coach, Andrew McKay, told her minutes before a competition that she would have to either dive or not swim in the meet.

Panicked, she took some practice dives. On her third try, she broke her neck.

Kahn, who spent three months in a hospital, sued the coach and the East Side Union High School District. Both a trial judge and a state appellate court, relying on the 1992 standard set by the state Supreme Court, tossed out her complaint, ruling that being injured during a dive is a part of the risk of competitive swimming.

In reversing that decision, the high court noted that most injured athletes -- including Little League baseball players hit by a wild pitcher or struck by a ball while playing on an unlit field at twilight -- have been barred from suing. Courts have even concluded that someone killed during a rock climbing class or ski rescue clinic cannot sue because death is part of the assumed risks.

But in this case, the court said there was clearly a legitimate question as to whether the swimming coach had acted recklessly in failing to teach Kahn how to dive and breaking a promise that she would not have to dive.

The justices noted that a veteran water safety instructor had testified that diving into 3 1/2 feet of water from a starting block is extremely dangerous if the swimmer hasn't received adequate training. A Red Cross training manual issued similar warnings.

Kahn's attorney, Patrick McMahon, said his client was delighted by the ruling. Although she can walk, he said, she has limited movement on her right side and occasionally gets splitting headaches.

"It will be a rare situation where a coach would be negligent as this guy was," he said.

Mark Davis, the San Jose attorney for McKay and the school district, insists that Kahn did receive instruction on how to dive and was never promised that she would not have to dive in a race. He said he was confident they would prevail in a trial.

"At least the court has set a high standard that seemingly will make it difficult for plaintiffs to prove liability against a coach or a school district," he said.

Coaches interviewed Thursday said they felt confident of their own training,

which emphasizes making student safety a priority. However, they said, injuries do happen, and any increased vulnerability to lawsuits would make them nervous.

"As a coach, we're not really compensated that much," said Michael Hutchings, head coach of the junior varsity football team at San Francisco's Washington High School, which is in preseason practice. "You do this out of love of the game and for the kids," he said.

"Football is a collision sport," said Frank Lee, a police sergeant who is head freshman football coach at Sacred Heart Cathedral Preparatory high school in the city. "We emphasize safety, but what can you do if you teach a kid not to drop his head, and he gets on the field and does it?"