Student of PSLE 2012 wrote:
I have listed out my 6 choices.
1.NANYANG
2.NATIONAL JUNIOR COLLEGE
3.ST.NICHOLAS IP
4.SINGAPORE CHINESE GIRLS SCHOOL IP
5.ST NICHOLAS O LEVEL
6.SINGAPORE CHINES GIRLS SCHOOL O LEVEL
Please help me as it's very urgent!

Given that your T-score is 252+3, I would say your chances of getting into NYGH is zero (last couple of year's COP was 262). Your chances of getting into NJC are also slim, given that the COP was 258/257 last couple of years and your T-score is only 252 (HCL bonus points cannot be used at NJC).
SNGS and SCGS IP are both new, so no one can concretely predict the chances. But I would say that you stand a fair chance of getting into SNGS IP with 255. Your chances of getting SCGS IP with 252 are fair to low.
I think you should be able to get into SNGS and SCGS O level.
So, realistically, I would tell you to drop NYGH or NJC from your list and add a safe option as your 6th choice. Have you considered MGS IP and O level?