The instruction has always been 150.
But ask any Chinese teacher, and a PSLE student, 150 words will barely get you a pass.
To get 80%, try to get your child to write up to 800 squares (each punctuation mark in a square).
Having seen my children moving from PSLE to O Level, i realise that primary Chinese teachers are really very "kiam-siap". To get 32 or 34 out of 40, is akin to getting the sky from them.
The same compo that gets 32/40 in primary six exam,
can get 28/40 in a secondary 2 exam.
Would you believe it? As long as keep to the topic and not 'out-of-point'.