Working Ahead of the Class

I have been trying to find a balance with teaching math to students who are at a variety of levels.  To further complicate matters, they have different learning styles.  As I reflected back on my own experience as a student in the intermediate grades I remembered my grade eight teacher who let a friend and me work ahead at our own pace.  I was incredibly motivate to stay ahead of the class, and probably worked twice as hard as I would have if I had been forced to work at the classroom pace.
I decided to allow my students who had achieved at a level four range for the latest unit get an outline of the upcoming unit and work at their own pace.  I felt that it would allow me more time to work with those who were struggling.  Right away, those not invited to participate were upset (even in tears).  I felt terrible about it.  I had tried this new format hoping that it would help everyone.  Curiously, many of those who were not invited to move ahead got a copy of the work from a friend and were determined to show me that they could work at their own pace too.
Beginning the next unit, I decided to give everyone a copy of the outline.  I told them that the conditions were that if they worked ahead, they could only ask me questions when I was done a given lesson and when those on the current lesson were comfortably working.  I found lessons went far more quickly, students came prepared with a question or two that was troubling them.  I had far more time to work with individuals and pairs at the white board.  Many students even completed sections that were not assigned, in order to improve.  The unit was Algebra, which I have found in the past to be tricky for many kids.  I believe that the test that the class just finished is perhaps the best one the class has written overall.  About half achieved a solid level four.  The bulk of the rest were in the high level three range.  I am still fine tuning how to allow freedom and teach a lesson.  I am worried that the excitement may wear off, but I remember how driven I was to work at my own pace.  I have begun this next unit having given them the outline.  I look forward to seeing the results.