Depends on the level
Most of the HA D3’s don’t redshirt. The “non HA” D3’s do, sometimes.
Its much more common at D1’s and D2’s. Go through the rosters and it’ll tell you. “Redshirt Sophomore”, “Redshirt Senior” etc... if you do your homework on specific schools your son is interested in, the rosters will tell you a lot. (If you do, let us know please what you find out). I haven’t really been studying the rosters of D1’s and D2’s in the last 18 months or so, because my son is very unlikely to play at that level.
An educated guess is that Redshirts will become even more common as a way to deal with the pandemic’s effect on creating roster logjams
JUCO’s are starting to redshirt kids more often now, too...