I don't agree that a student taking a specialised course in poly would learn less.
Some of the more specialised course in poly really helps to pave the way to Uni, such as accountancy, computer or marine engineering...
For those who has got good results, congrats!
For those who did not get as good results as expected or would like, don't be discouraged. O Levels is just a milestone in life to pass. If you're to go ITE or Poly, continue to strive to do well. I've met people who strive all the way from ITE to Poly then to Uni and have done very well.
Slow and steady wins the race.
In fact, for those who are at a lost, think about what you do best and how your character or personality would suit a certain line of work. Then choose a course that would provide the knowledge, skills and qualifications to suceed. That is one way to know which course to take.
However, how does one know to go to poly or JC (and subsequently Uni?). There's another issue to consider.
Actually, our education system is really limited. If you don't do well in O Levels, it might not be an intelligence issue. It could be due to the limitations of the teaching and evaluation on learning, i.e. your learning style is different from the education system and hence you cannot perform your best in the evaluation (O levels in this case). Hence, get to know the learning styles and determine your learning style.
http://en.wikipedia.org/wiki/Learning_styles
http://www.learning-styles-online.com/overview/
http://www.engr.ncsu.edu/learningstyles/ilsweb.html
Once you get to know your learning style, then you might wanna think about how the ITE, Poly or JC is suitable for your learning style.
I remembered that I felt suffocated in secondary school and JC because the mode of teaching and subjects were so dry and memorisation is not my strong point which is required to do well in those days. I went to Poly and was totally liberated! I love doing projects, going for lectures and doing tutorials because of the practicality of the assignments. I had a blast in poly.
When I did a learning style inventory later on, I realised that my learning style a cross between abstract conceptualisation and being hands on. Then, I understood why I thrived in Poly.
Hope this helps!