Law schools attended by SCT Justices in 1978, 40 years ago:
2 Yale, 2 Harvard, 1 Howard, 1 St. Paul, 1 Wash & Lee, 1 Stanford, 1 Northwestern
Law schools attended by SCT Justices in 2018, assuming Kavanaugh confirmed:
4 Yale, 4 Harvard, 1 Harvard-then-Columbia
Why the change?
2 Yale, 2 Harvard, 1 Howard, 1 St. Paul, 1 Wash & Lee, 1 Stanford, 1 Northwestern
Law schools attended by SCT Justices in 2018, assuming Kavanaugh confirmed:
4 Yale, 4 Harvard, 1 Harvard-then-Columbia
Why the change?
2/ I think there are a few explanations. First, there is more of a national market for law schools today. Students from anywhere more likely to apply to the same schools.
3/ Public scrutiny of SCT nominees is much more intense than it was a half-century ago. A nominee's having attended a brand-name school sells to the public as the nominee being smart. (Only smart people went to Harvard, right? Um, no, but it sells easily.)
4/ Expansion of the # of law clerks per Justice (each gets 4 per year since the '80s) has produced a large-ish set of SCOTUS-experienced insiders who get the Court & are known ideologically. W/Kav, 5 of 9 Justices will be former clerks. Clerks often from brand-name schools.
5/ Also, there have been major changes in the politics of SCOTUS noms. Activists want a thought leader for their side, who will influence the law for generations, not just vote a particular way. On the margins, academic credentials can bolster that case.
6/ Finally, some of it is just idiosyncratic or random chance. According to news reports, at least, Trump loves Harvard or Yale credentials. If the President values it, you'll see it in nominees. Anyway, all just my speculation. /end
7/ Wait, one more: @StevenJDuffield brings up the excellent point that in the old days, the politics favored regional representation. Different seats often linked to different regions, and that often meant different law schools. en.wikipedia.org/wiki/Demograph… 
