Haha... I went overseas to study after NS. Even worse, not only
were the girls in my class more current, the boys were as well.
This was in the UK. And bear in mind, they are even more current
than our Singapore A level cohort, because the UK system finishes
their A levels in the summer of the year of entry ( i.e. in May or
June of the same year that they enter in September !).
I did Engineering and I suffered because my maths was rusty.
Maths you need some practice. The other subjects were easier, as it
was a matter of reading , which you also can do during your NS
stint. For me, I bought some physics and chemistry books when I was
in ROC and read them before ORD. At that time, the bookshops there
were printing very cheap publications of Western textbooks.