[Grammar] had missed the chance / missed the chance

[Jokies]

Mr C. was a very honourable man. He donated large amounts of money to a school for illiterate adults who had missed the opportunity to learn to read when they were young.

Is it grammatically correct to use the simple past ("missed") instead of the past perfect ("had missed") in this sentence?

 

[GoesStation]

I'd stick with the past perfect because missing the opportunity occurred before the adults would attend the school.