80's or 90's movie designed for children about a group of boys and a girl wanting to join them

I vaguely remember a movie about a group of boys that hung out together on a playground and a blonde girl wanting to join them. The only thing that stands out in my memory is I think towards the end of the movie the boys go off and do something and leave the girl behind and she ends up falling off some monkey bars and landing unconscious. I think she may have diabetes or something. When I was little I watched it a hundred times on VHS but cannot for the life of me remember what it was. It's not the Babysitter's Club or the Sandlot. The kids in the movie were probably around 12 or so. Any suggestions would be great. I was around 9 or 10 when I would have been watching this so that would have put the year around 1989/1990 (but that doesn't mean it was made then). Any suggestions would be greatly appreciated...I'm going nuts trying to find this movie.