What matters is the continued good reputation of the school among recruiters.
Some lawfirms do look at USNEWS. I had a friend at UMich who did a summer associate gig in Cali last summer. He said the recruiters at his firm really paid attention to the usnews and wouldn't really look at people outside of the T20 except for the top top top student(s). Some firms may do internal, some may not but I think the power of the (evil) USNEWS rankings can't be underestimated. That being said, this only matters for a very very small segment of the legal community. The vast majority of firms don't even use summer clerks to recruit, they have year round clerks or just post at a local law school. At many of these firms it is possible to make just as much $ if not more than at biglaw. Maybe not in starting salary but in the long run.