There is a "high incidence of severe injuries" to rugby players at schools in Northern Ireland, according to a major new study from Ulster University.
The research explored the types and causes of injuries in schoolboy rugby.
Almost half of the injuries suffered led to the player spending at least four weeks out of the game.
Ankle or knee ligament damage was the most prevalent type of injury, but the researchers also found relatively high levels of concussion.
A total of 825 schoolboys from 28 schools teams took part in the study during the 2014/15 school year.
The players were older boys playing for schools' first teams.
More than one in three of them suffered at least one injury during the season.
The researchers recorded 426 injuries in total, of which 204 resulted in an absence from the sport for longer than 28 days.
While sprains were the most common injury, about one in five injuries were due to concussion.
This equates to about three concussions per team, and the researchers said that "these figures are higher than most previous reports in youth rugby".
They also warned: "Young athletes are more vulnerable to concussion and may be affected by more complicated recovery times and higher risk of adverse outcomes."
However, the report said young players were adhering to concussion guidelines produced by the Irish Rugby Football Union (IRFU).
"Ninety-six per cent of players returned to play after a minimum of 24 days, which is consistent with the 23 days minimal graduated return-to-play guidelines of the IRFU," it said.
The research also found that most injuries happened during tackles or collisions and that heavier players who did a lot of weight training were more likely to get hurt.
The study suggests protective equipment like shoulder pads or head guards did not reduce the risk of injury.
Chris Bleakley, the study's lead researcher, said there was "no magic bullet to all of a sudden reduce injuries".
But the report had found areas that could be looked at to help prevent players from being hurt, he added.
"Enforcing the laws of the game is definitely one, that's things like looking at the height of the tackle, ensuring that it's interpreted properly, and teaching good tackling technique," he said.
The Rugby Injury Surveillance in Ulster Schools (RISUS) study was partly funded by the IRFU and Ulster Rugby.