Group Photo that I need to create transparent background
I have a group photo of about 70 kids sitting on a gym floor. (I actually have 7 of these types of photos that I need to do.) I need to get rid of the gym floor in all areas - on the edges and in between kids. I have tried the masking option, the magic wand, and the background eraser, and none of them are working well. With the background eraser, it is leaving a dirty look around the edges - like it's only erasing part of the background and leaving "residue". It also doesn't work where the gym floor has black lines and the kid near it is wearing a dark shirt or has black hair. It also leaves a small edge of color around the edges in some places. The masking is a problem because I can't seem to accurately draw the mask around the kids. I don't know if I need a different brush, or if I just have to do it slowly by hand, nearly pixel by pixel in some areas. I also don't see how this option will remove the section of the floor in between the kids. The magic wand causes the same problems with kids wearing similar colors next to the black lines. I am using Photoshop Elements 9 and I'm very inexperienced with it. Any help would be great. Here is the photo:

