Dogs coming out of shelters often have a number of issues. Frequently they lack confidence, have little to no body awareness, and may not even know how to learn. By starting to interact with a shelter dog through basic foundation agility, dogs progress quickly as they learn to play on low equipment.
The first skill I usually teach a dog is how to put his front feet up on a pedestal (rubber feed pan.) This is taught by shaping the behavior, allowing the dog the freedom to experiment, make mistakes and figure out how to earn a reward. Once the dog is proficient at getting up on the pedestal, the next step is learning how to maneuver his hind legs around the bowl without taking his front feet off of it. This accomplishment teaches rear end awareness and starts to build coordination and self esteem in the dog.
Dogs are situational which means that they learn in the context of where you teach them. Just because a dog can perform a task in one location (for example in your kitchen) does not mean he will understand the concept if you ask for it outside in the grass. Learning must take place in many different locations before a dog learns to generalize the exercise. People, usually generalize what they learn easily, dogs do not.
As dogs learn more and more, their ability to generalize grows. The shelter dog, with little to no experience learning, should not be viewed as slow or stubborn simply because new places make it difficult for him to perform.
Patience, consistency and training in many different places will produce the best results.