How different should my Statement of Purpose be from school to school? I'm preparing for my (second round of) grad school applications, and as such I am (re) writing my Personal Statements and Statements of Purpose. I am already tailoring them to the specific school I intend to send them to - in the sense that I make sure to reference the correct school, their location, professors therein, etc. What I am wondering is, how much of my statement should be specifically written with this school in mind?

Currently, a large part of my statements are quite similar - these are my academic qualifications, this is the research I have done, this is what I learned, this is how it's applicable to my graduate interests, etc. In a 10 paragraph statement, only the first paragraph and last two paragraphs directly reference the university I am intending the statement for. Is this sufficient? Or should I be creating each statement from scratch and linking every element in it to the university I am applying to? Something in between?
You may be making a mistake in writing about the past in your SoP. Your accomplishments are probably detailed elsewhere. Make the SoP forward looking, what you intend to do in the future, including beyond grad school. Mention your past work only so much as it directly supports your suitability for the degree and field you wish to pursue. 

For a doctoral studies application, I don't think you need to tailor it too much unless there are specific working groups that you want to join. Then it is a good idea to mention them and also to mention professors that you (truly) know something about and might want to study with. And, of course, if you are applying to fundamentally different programs, such as in different fields, you need to tailor it to the specific case. 

Later, for job applications, the SoP should be more closely tailored to the job as described in the call, but not so much for continuing studies. 



Caveat. If there is nowhere else to mention your accomplishments then, of course, the SoP is the place for that. But don't just repeat what is easily available elsewhere.