This is a photo of our dog Mungo (a Heinz 57 with some pitbull/staff in him) , some members on here have met him and know him to be, like Rick's dog, a lovable and peaceful dog who wouldn't harm a fly (except the Postman). Despite that, I won't let him near children unless he's on a lead, nor will I let him near any other dog because he would fight until serious harm was done. He came from Fred Scales' rescue place at West Hougham and was quite clearly raised by an owner who trained him to be aggressive; the studded collar gave it away, but when we first got him he would pick a fight with anyone, and we had him neutered to try to work some of the testosterone out of him.
Six years down the line, he's now a perfect a dog at home and very friendly to the majority he meets, but he cannot be trusted near children or other dogs. Knowing this, he's fine, but I do keep him on a tight lead if and when he finds himself near kids, just to be safe for child and dog alike. There is probably nothing to worry about - a friend visiting from Japan brought her 14-year old with her, whose first reaction upon seeing him was to fling her arms around him and give him the biggest hug you ever did see, and any suspicion he may have had about her vanished. On another occasion, visiting my wife's Godson in Blackpool (he's 8 now, 6 at the time), the lad actually got into the dog's bed in the back of the car and pestered the dog to death; far from any aggression, Mungo scarpered as quick as he could! Such was the effect of a tearaway boy on him! That aside, he does seem a lot calmer in general with kids around him, but one never knows the history of rescue dogs, and in Mungo's case I would much rather be safe than sorry. I'd be devastated if he hurt a child, both for the kid's sake, and for the fact that I'd probably lose Mungo too.