Josh Ferguson pocketed two first-half scores as Tom Magill’s Wildcats (17-2) shrugged off an early score and powered back for the win at Lower Dauphin.
Jarrett Fortenbaugh and Tyler Fegley also scored for Greenwood, which fell in last year's 3-A title game at Hersheypark Stadium to York Catholic.
The Wildcats, who bagged their ninth consecutive victory, will play Lancaster Country Day in a Tuesday semifinal at Cumberland Valley.
Luke Leinbach staked High Point (12-6-1) to a 1-0 advantage in the second minute, but Ferguson sandwiched his two scores around a Fortenbaugh finish were sporting a 3-1 lead nearly 22 minutes later.