Freelance
The majority of the native English speakers who teach English in Madrid come to Spain to learn the language and the culture. They resort to teaching and translating as the only source of income available to them. In spite of this, many companies still contact their local academies and language schools to arrange classes for their employees. If they are lucky enough to get a good teacher it's very unlikely that the person will last very long because the best teachers always end up opening their own schools or working for themselves. Freelance teachers, on the other hand, are better qualified and highly motivated. As permanent residents they can make long term commitments to their clients. Self employed professionals try harder to satisfy the customer because their future and reputation are at stake. Hiring a language teacher should not be like calling a plumber. It must be a long term commitment.