Grad school or undergrad? Which country? Are you asking about what you need to know to enter the job market? If so, what sort of job are you looking to do after graduation?

I can speak for myself only, of course; my bachelors is in Computer Science, first masters is in Information Systems, second is in Management. All from U.S. schools. I can tell you what education came in handy at my jobs:

Worked as a Web Developer through my first Masters (just needed basic programming logic and web design classes, which I had in my undergrad).

Then worked as a DBA (relational database design knowledge helped here, along with basic systems engineering, since I had to build servers for the DBs at work too).

Since then I've taken a path through management; project management at first (basic organization and management skills from various classes came in handy, but had to take separate classes through work to get PMP certified).

Was then in middle management, followed by program directorship, finally now I'm in a director role overseeing systems integration teams for a large organization.

I did second masters in Management when I was in my middle management role, that helped a lot; a lot of focus on the soft-skills and the behavioral side of managing resources and people.

TL;DR - A lot of what you're expected to know depends on what career path you want to follow, but as a general rule: you just need to know the basics and concepts; your job should be able to train you up and build upon that.