A school in my district that is piloting full inclusion (really, truly full inclusion - with the exception of students with such significant mental health needs that safety can't be maintained) gets regular training sessions from my office. The training that is at the top of their list is how to balance the needs of exceptional students with typical students. On the face of this question is a concern that we all have as teachers: How do we meet everyone's needs given the limited amount of time and resources we have. This is a fairly universal problem.
However, it seems to me that this question always implies from the asker an answer (you can't) and a course of action (those kids should be taught by someone else). It doesn't seem like a pure request for guidance. Maybe it says something about me that I view the question as insidious and disingenuous but that's the way I see it.
I think you answer this question with the following two-pronged approach:
1) Students with special needs have...special needs. By definition they take up more of our time. This is only fair if we accept that everyone should get what he or she needs. Until we accept that students are truly different and require different amounts of time spent on them, we'll keep hoping the high needs students disappear. This is the philosophical approach to answering the question.
2) We can be sure that students with high need are going to take up a lot of time one way or the other. The thing that we can do to mitigate the feeling of being overwhelmed is by deciding when we're going to put in the time - beforehand or afterward. Fortunately we get to decide whether we want to spend the time preparing so that during class the student has a better chance of maintaining without an exceeding amount of attention or putting in the time during the activity or what have you because we failed to prepare. The choice is ours. And obvious. This is not to say that we can always anticipate the needs of students but we often can and choose not to. Part of good practice is attempting to cover all the possibilities for what might happen - checking the equipment out ahead of time, having a back up plan, keeping extra, relevant work at the ready for someone who finishes early, willing to be flexible to accommodate bad days, etc.
So I feel like I can give a 5 minute training on this. But they gave us an hour so we're going to the planning piece to the next logical level: differentiated instruction. This is not really happening in ours schools even though we're moving full steam toward more and more inclusion. Without differentiated instruction we're just using band aids. More on this later.