In 2014, what was the approximate internet penetration rate for individuals that have attained less than a high-school education

The answer is "75%".

The Internet Penetration Rate communicate to the level of the aggregate populace of a given nation or locale that uses the internet. An internet user is defined as anybody in ability to utilize the web:

(1) The individual must have accessible reach to a internet

(2) The individual must have the essential learning required to utilize internet tools.