That link I posted also shows the precentage of each class that clerked after 3L. I don't think it differentiates between state and federal programs. I'm interning in Federal court now and the judges I've asked here say they pick clerks based on their resume, GPA, and writing sample, what school they went to is often not a factor unless they hadn't heard of it. The federal judiciary is filled with judges from every school and so they understand that not every good applicant went to HYorS. In fact, the judge I work for now went to Stetson. That being said, the numbers show that a larger precentage of students from prestige schools land clerkships.