I think the l-dropping phenomenon, which I've heard even among educated kiwis, arises from the fact that in New Zealand English, lip-rounded vowels are pronounced differently if l follows. The vowel in school is a high back vowel, while that in scoot is a high central one. Similarly, the diphthong in coal consists of a middle back vowel gliding into a high back one, while that in coat consists of a low to lower-mid central vowel gliding into a high central one. If the l is dropped, the vowel sound still conveys the impression of a following dark l, even to the ears of a non-l-dropping kiwi. In these instances, l is dropped rather than replaced with w. When l follows a non-lip-rounded vowel, l-droppers replace it with a high back lip-rounded vowel sound. It is probably misleading to represent this as w, as the consonantal w does not involve the raising of the back of the tongue in NZ English. —Copey