If you are up to 8 credits short to gain University Entrance and would still like to start University Semester 1 2019, Hagley College is running a catch-up programme. For further details check out their website and get in touch with them ASAP.
Another option is Te Kura Correspondence School. Through Te Kura you can study for free if you are between the ages of 16-19 years and a NZ Citizen or Permanent Resident, currently living in NZ. For further information check out their website and get in touch with them on 0800 65 99 88.