DPA ("Direct Polytechnic Admission") gives O Level students a
priority over other students applying through JAE.
So if you apply for DPA, if you get shortlisted, you will be
called down for an interview and some courses may require you to
sit for an apitude or skills test.
If you are accepted, it means you already secured a place in the
poly's course. So as long as your O Level is within the course's
and the DPA's minimum entry requirement, you will get a place in
the course. Certain polytechnics may have different crtieria and
requirements for DPA students, some may require students to attend
camps and extra lessons before school starts for other ordinary O
Level students.
For example, if the cut-off-point is 10, and you get 16, you
will still be able to secure a place as long as you fulfill the
minimum requirement for DPA.
Check up SP's DPA system.