Anything less is simply not as effective. It is humanly impossible for any one or two people to be able to manage this kind of intensity over any significant amount of time without burning out. A team approach is the only reasonable one. As stated above, motivation is key to working with autistic children. Not only must there be strong external motivation to attract the autistic child toward our world, but that motivation must be as pure as possible.
Volunteers are unique in the purity and intensity of their altruistic motivations.
They want to reach outside of themselves to help another human being just for the sake of doing so, because it is good, and because they are needed. Volunteers fall in love with the autistic child naturally and easily, developing high hopes and expectations that inspire the parents, professionals, and fellow volunteers in a way that only they can. The reciprocal relationship that develops between the volunteer and child is priceless for that child's future interpersonal skills. Volunteers make that one child whom they teach the focus of their efforts and learning, whereas any professional is necessarily divided amongst a caseload of children. Volunteers have faith that their efforts will make a difference for this child.