отличник.... In the US, is an "A Student" or a "Sraight-A-Student" or "4.0 Student".
The grade-point average (GPA) of this student is 4.0,
A student who has a 3.7 to 4.0 GPA is a High Honor Student.
A student with a GPA from 3.5 to 3.7 is an Honor Student.
The student with the highest GPA at graduation is named the "Valedictorian" and will give a speech at the graduation ceremony.
ударник......the most productive worker is sometimes called the "top worker", "top salesman", "top manager", etc.
Often there is a vote taken by the workers or managers of a company for the "employee of the month" or the "employee of the year". If you are chosen the "employee of the month", you often receive a bonus-- usually money.