My daughter graduated in July this year. Firstly, both SPCC (St Paul's Co-educational College, I guess) and DBS are Direct Subsidized Schools. In other words, they don't join the central allocation (lucky draw). La Salle is Gov't subsidized school, however.
My daughter's class (6A) has at least 3 boys who're now studying at DBS. They're very smart and all-rounded. Those who are now studying at SPCC are good too. The overall position
If you want to know more, you can discuss with the class-teachers. They may tell you the past record of students who had similar academic performance.