To see the effects of environment you only need to go to a 3rd world country... Reading is a skill that is generally taught (and very difficult to learn without being taught), so when someone is illiterate, it greatly affects their ability to learn anything. Likewise, people CAN overcome their disadvantages, depending on how severe the disadvantages and how motivated (overcoming negative parents is easier than overcoming illiteracy and being forced to labour in a sweatshop at 10 years of age)...

This article is merely a less extreme example of how taking an active interest in your child's education can help them develop, which is 100% true. For me, personally, I could read/write/speak 2 languages at 4 years of age, in large part thanks to my early childhood environment.