Student or Learner
The more and harder students work, the more impression on their employers and colleagues they make, establishing the foundation (can I say "ground" here?) of a future promotion.
I do not really like the last part of the sentence. I want to say that student can make a good impression on their emplyoers and colleagues if they work hard enough. And it can help them (students) to earn a reputation which will help them to get promoted.
Please, correct all my mistakes. I should know English perfectly and if you show me my mistakes I will achieve my dream a little bit faster. A lot of thanks.
Not a teacher nor a native speaker.
"The longer and harder students work, the stronger the impression they make on their employers and colleagues, thus establishing a greater likelihood of a future promotion.
You can say, "... establishing the groundwork for a future promotion."