First, a warning: These techniques are only to be tried on durable fabric or as a last resort before throwing the clothes out.
Over the years, there are two methods I have used for getting stains out of white fabrics. Both these methods are pretty harsh and could potentially damage the fabric. However, they often also work. Look at the item and figure out if it is worth the gamble to see if either of these methods will help. They work quite well on cotton and I have never tried them on polyester (like uniforms) because I am scared.
Recipe #1 involves taking 1/2 cup of powdered Clorox 2 bleach, 1/2 cup of powdered All laundry detergent, and 1/2 cup of Cascade dishwasher soap. Mix together and dissolve in a large bucket or laundry tub. Soak the fabric in this mixture, checking every 20 minutes or so to see if the stain has been removed. Rinse well when the stain has come out, and wash separately or with whites only the first time.
Recipe #2 isn't even a recipe. I pour about a cup of Cascade in the washing machine in lieu of the laundry soap, add the clothes, and after allowing it to agitate for a few minutes, let it sit for several hours or overnight. I do this weekly with my white towels and bath mats. It is the cleanest they ever get.
For more laundry stain ideas, see Laundry Helpers I Love.