Why are these food banned in school?

Fattening food such as nugget and french fries are banned in school canteens but nasi lemak is allowed to be sold.  What logic is this?

Nasi lemak has calories of 644 while a piece of chicken nugget is 48 calories whereas french fries (say small serving of 85g) is 271 calories. Even if a child eats 5 pieces of nugget and still have the stomach to take another serving of french fries, calories count is only 511, still less than that of a packet of nasi lemak.

Realistically, with just about 15-20 minutes of recess, a primary student may most likely buy either nuggets or fries and not both western food (queueing up time has to be taken into consideration).  So, the calories count will be most probably less than 511 . Comparing this to a smaller serving of nasi lemak (which a child can normally take), the difference is not that significant.

So, I still don't see a better rationale to ban the western food but not the coconut rice.