I know this topic has been discussed before and I am not advocating a older or younger age to start kids riding but I want to share my experience today as something to think about. I took my son out today for a ride he is 12 soon to be 13. He has ridden since he was 10. However due to my heavy weekend work schedule the times he have gotten to ride are limited. I decided this time to put him on a Yamaha Vmax 600 136 track for trail riding only. I usually have him on a 340 Yamaha Enticer but since he has grown to 5'5" I thought he was big enough for the Vmax. We left the cabin and got 3 miles down the trail when I noticed he was no longer behind me. I turned around and found him sitting in the snow dazed and the sled smashed against the tree. His helmet visor was shattered. I had him get on my sled with me and took him back to the cabin. He seemed fine but was shooken up. I determined latter that he has no memory of the accident and the ride back to the cabin (5-10 minutes). He remembers his visor being covered in snow not being able to see and waking up in the cabin but nothing in between. I took him to the ER to be checked out and they said he had a mild concussion. We are watching him close tonight. It looked like to me that he got too close to the edge of the trail and got sucked into the soft snow which covered his visor and he panicked grabbing the throttle instead of the brake launching him into a large spruce tree totalling the sled. I have heard the argument many times that some of the kids are excellent riders which I do not doubt. However this scary lesson reinforced what had or should have known that the young riders do not have the life experiences and critical thinking to correctly react to unexpected situations. At our trail speeds 20-25mph and the distance from where he left the trail to the tree was more than enough to completely stop the sled. I am not going to judge others when to start their kids on snowmobile but I am going to evaluate how, where and on what my son rides in the future.