In recent days, there have been notes about the New England Patriots and members of their coaching staff visiting schools to work out perspective draft prospects.
It's not uncommon for coaches to visit schools and work out particular players. As a matter of fact, it's exactly what coaches from each NFL team are doing around the league at this very time.
It's important to keep in mind the context of these visits: in some cases, there are under-the-radar prospects that teams haven't seen much of. In other cases, there are players that the team has identified as potential fits that they want to do more homework on. Sometimes, these visits are a matter of convenience, as could be the case with Bill Belichick showing up at Central Florida recently, as the school is located near the site of the NFL owners meetings.
Coaches have only seen game tape of the draft prospects, which is a critical but not all-encompassing method to evaluate them. School visits afford them the chance to pick the players' brains on football intelligence (as they did at the combine), and also get a better view of their body types, something that can be harder to decipher when they have pads on (as an example, some coaches took note of Louisville quarterback Teddy Bridgewater at his recent pro day. He is considered a slender player for a pocket passer).
The pre-draft evaluation process is inexact. The Cowboys infamously traded up for LSU cornerback Morris Claiborne back in 2012 after having no contact with him.
Other times, pre-draft visits and workouts lead to teams investing in a player.
The takeaway is, while these workouts and visits can impact the evaluation process, they are just one piece of the puzzle.