University Entrance isn't a sure thing. Even if your teen passes NCEA Level 1, 2 and 3 with flying colours there is still a chance they wont gain University Entrance (UE). The national average for students failing UE in 2014 was about 60% - don't allow your teen to fall into this percentage. Even if they don't want to go to university, gaining UE will keep their options open.
Before starting NCEA every student should understand the requirements to meet UE and they should track their progress throughout the year to make sure they are meeting this criteria.