Elitism rears its ugly head - Poly student with near perfect GPA refused admission to top universities

The following post by an anonymous writer is republished from the Facebook page 'NUS Whispers'.

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I'm currently a poly grad who graduated with a 3.93 GPA, bronze medalist in Business.
Applied to NUS, NTU, SMU, SIT and UniSim.  However, was only accepted by SIT. I do not intend to accept my place in SIT as I am aiming for the top 3 Us. I also do not intend to start work.

Am terribly distraught and wondered what went wrong as I'm sure I've met all prerequisites and have a fairly impressive portfolio with better than decent O level grades.
There is also a handful of my poly friends in the same boat as me and we thought that this may be because the local universities may give preference to A Level holders.

Hence, I want to know if this might be true. And if it is, how should I go about taking the A Level preferably in 2017 or 2018. There's a handful of my poly seniors who've done this and have made it into NUS. Sadly, they're uncontactable now.

Any advice where to take cheap/heavily subsidised night classes conducted by MOE or government affiliated centres? I understand MOE conducts night class for O level repeat students and was wondering if they do the same for A Levels.

Do advice. Thank you!!