How should PhD student show importance of research proposal in cover letter requesting access to important dataset? I am a PhD student,  and I am applying to be part of a cohort of graduate student researchers who will be using data from a national survey (that everyone in my field wants to get to) to answer policy questions. The dataset  will most likely be a part of my dissertation.

The application requires a cover letter that needs me to explain certain parts of my research. 

Here is what i wrote:


  My current research interest is concerned with the interactions
  between families, students, teachers and staff in Head Start programs;
  specifically families who frequently encounter structural barriers due
  to their race, ethnicity and/or limited English proficiency. This work
  is important because of many reasons, but to name a few: the current
  climate of uncertainty experienced by families from diverse
  cultures/ethnicity/nationalities and how it pervades the education of
  their children, the forecasted minority/majority shift our population
  is going under and the overall right to equal access afforded to every
  child in the United States. I believe my work will contribute to a
  better understanding of the barriers these families confront on a
  daily basis and to a dialogue about practical solutions in the form of
  policy changes in order to ameliorate said barriers


I asked my adviser for feedback, and she said


  You have said why the work is important and how you will contribute.
  But from what you have written, I do not know what it is that you are
  doing that will contribute to the field. What is your research,
  exactly? Why is your study, specifically, important?


I am really not getting it. I have been grappling a lot but i end up writing things like my methods. Any way you can illuminate will be appreciated.
Your advisor's critique is exactly right.  You've made a convincing case that your subject is important, but not that your work is important.  This:


  My current research interest is concerned with the interactions between families, students, teachers and staff in Head Start programs


is the sort of vague writing that a lot of academics are prone to (I'm always trying to beat it out of my writing).  Being "concerned with the interactions" is a very abstract, high level statement that doesn't actually say anything.  Concerned with how?  Which interactions?

Finding out whether teachers say "hello" or "hi" more often to family members is an investigation of the interactions among the people you describe, but it's an utterly uninteresting one.

Start concrete, with the specific research questions you plan to ask.  Think about what you excited about your research. How would you describe your work to a non-academic? What's the story you that keeps you excited about how your research will actually matter - the line of causation from the work you're going to do to actually making people's lives better?