It took Selborne until the 20th minute of the match to break through the St Andrew’s defensive line, with winger Miles Norton going over for the first try.
The visitors’ forwards began to dominate the physical clash, and Norton’s second try gave them a 14-3 lead at the break.
St Andrew’s hit back early in the second half with a try from outside centre Matthew Moore, who would get another later in the game.
But two more Selborne tries, from flanker Alex Greig and scrumhalf James Bruce, were enough to secure the win.
Eastern Cape results (21 May):
Graeme College 14 Grey High 52
Port Rex 20 Kingswood 49
St Andrew’s College 17 Selborne 26
Woodridge College 10 Humansdorp High 28
Photo: St Andrew’s College