Does Intelligence Equal Learning Ability?

As every teacher knows, in any normal classroom and whatever subject is being taught, there will be a wide range of individual differences in students' learning. Some will learn more quickly than others; some will retain more. Whether learning is measured by results on achievement tests, by the number of units completed, by time taken to progress through a set programme, or by the amount of material recalled at a later date, these differences will occur. Often it is the same students who repeatedly do better no matter what the subject, but sometimes surprise's occur and a child who was thought to be somewhat dull will suddenly shine on one particular task.
So is there a single trait called learning ability, and if so, is it the same thing as intelligence? Do the more intelligent students always learn better than the less intelligent?