In New Zealand most students leave school at the end of ‘Year 13’ (final year, usually age 17 or 18) or sometimes ‘Year 12’ (second last year, usually age 16 or 17). The New Zealand qualification is called ‘NCEA’ and ‘Level 1’ is covered in Year 11, ‘Level 2’ in Year 12 and ‘Level 3’ in Year 13.
It's common for students planning on taking up a trade to leave at the end of Year 12/Level 2. In regards to tertiary education at a Polytechnic or an Institute of Technology ('technical school'), it depends.
Before doing an apprenticeship for a trade (for builders, anyway, I assume with other trades too), students take a 'pre-trade' course at polytech.
For other things taught at polytech, such as Nursing, Year 13 is helpful (Nursing students without Year 13 usually have to do a 'foundation' year at polytech).
Any students planning on going to University ('college') need to achieve 'University Entrance' which is done in Year 13 at the same time as Level 3. I would assume most/all students applying for uni would also have Level 3 too.
Leaving school after just Year 11/Level 1 is strongly not recommend, and generally considered a ‘lower-class’ ‘drop kick’ kind of thing to do. I would strongly recommend getting the full University Entrance and Level 3, unless you have a specific trade in mind. Year 13 is also supposed to be a really fun year where students bond as a group.