As long as you have the heart to improve yourself in secondary
school, you will definitely succeed one way or
another 
Getting below 200 doesn't mean you are an underachiever. Don't
let your parents' thoughts influence your own. You are your own
person, and you run your life, not them. It is possible to even
jump to express from NA if you're willing to study extremely hard,
though I don't recommend you do that because it's a very steep
jump. We all rventually take the same exams eventually, just that
NA has a 'N' level in between and an extra year.
Your parents called you "underachiever"? Prove them wrong.
Join a CCA, be very active in it, and maybe someday you might
even be promoted to Chairman or Vice-C if you're devoted/committed
enough. Capitalize on all opportunities to develop your leadership
abilities, especially from sec 1-3 - you'll have a lot of spare
time in those years until 4/5. Join all CIP the school offers, or
if you're interested (I was a librarian, peer leader, and
vice-chairman of my CCA in my 4 years and it really paid off). Do
external CIP on the side whenever you can (trust me, we all have
spare time, it's just that most of us don't utilize them
effectively). Examples include OCBC cycle, standard chartered
marathon etc, you get money AND cip hours on the side. Not
recommended to slack off your CCA because it gives you -2 points in
O levels (and that is really, really important) so make sure you
choose something you really enjoy if possible.
You may have heard this gazillions of times from others, but
don't mix with the wrong company. I don't even know you so I can't
dictate what's right or wrong, but I think you know what's best for
you and your future when it comes to deciding what kind of people
you want to hang out with. I've seen people get 250+ for PSLE and
yet end up with 16-20 points (net score) for O levels. You can be
the opposite if you try hard enough.
Best of luck. Remember, always have confidence in yourself;
don't let others pull you down. A confident man is a rich man.