t-score:Psle t score.
Alamak until now pple still confuse about t score. The t score is basically a rank score of where your result stand compare to others. If u hv 50 it means u hit the average score of the cohort. If you got 60 it means 15.9 per cent of the students did better than u n if you got 70 it means 2.3 per cent did better than u. If you got 80, it means 0.1 per cent did better than u!!! And every year it is the same! So assuming students ability r the same for all 4 subjects, if u got 280 it means 2.3 percent did better than u! That is why govt say 200 is the average score. But remember this is a rank score, not your ability of the subject. Moe hv set paper so that student has the ability to get a C meaning credible understanding by world std. That is why even student with less than 200 t score, they know their subject well n hence our student did very well in international bench marking. So look at the grades n be concern if it is not a C, it means the kid may not hv a good understanding of the subject. Then better brush up before going to secondary school. Dont forget at the end of the day we r competing against the world, not ourselves.
Since this topic is on top 10%, if the student get 62.7 it means 10% do better than him. Again assuming same std in all 4 subjects, if the student got 250.8, it means 10% do better. In other wordss top 10% score is >250.8, but that is assuming student is same std in all 4 subjects. But we know as a fact, not all top student (ie. top 10%) fair the same for all subjects, hence, every year the top 10% is for sure less than 250.8. That is why MOE says every year top 10% is about 250. For 2014 psle result, i had a friend who kid got 249 and receive MOE letter offering him 3rd language. So if MOE is correct, only top 10% would be offered, it means 249 may be the minimum. This website says 2014, top 10% score is 248, that may be true.
Also if your kid is top 10%, he/she will receive a MOE edusave scholarship of about $350. And yes, it goes to the kid edusave acct 
Your explanation on tscore is not really correct. Other than the tscore is a ranking system which is correct, the rest are not fully correct. Read up on tscore calcuation here:
http://www.greatminds.edu.sg/index.php? ... &Itemid=91
Top 10% changes almost every year. And it is definitely not what you stated \"every year the top 10% is for sure less than 250.8\". There are years when top 10% is above 250, though in year 2014 it is less than 250. As MOE don't show us the raw score of all students and also they don't tell us the Std Deviation, there is no way to tell what is top 10% from the t-score itself, the best guess is look at the cut off point for 3rd language been offered (i.e. French/ German/ Japanese/ Spanish).
And your statement - \"Also if your kid is top 10%, he/she will receive a MOE edusave scholarship of about $350.\"
Which MOE edusave scholarship are you talking about ? Edusave Merit Bursaries, Good Progress Awards, EAGLES, EESIS or others ? They all have different requirements.
Just want to clear up the misinformation.
Thanks.