"IT specialist" vs. "computer scientist"

I talked to my English teacher about what to name a person who works with computers. For Germans: Informatiker. As far as I know, the job is called "computer scientist", that's what most translators say. But my English teacher keeps telling me that the term is "IT specialist". "Computer scientists" are academic IT specialists, while the general worker is an "IT specialist".

Which is the correct form, now? When I should use either?

EDIT:
I need to clarify my problem.
I just finished my apprenticeship. As I said in my comment below, at the end of the apprenticeship, we all have the same degree, we are called in german "Informatiker". I made the apprenticeship in Switzerland, so maybe it is different in other countries. It doesn't matter if I work as a Java developer, so software engineer, or if I am working as a system engineer or, as oerkelens in his answer said, what ever you do in the nearly endless list of "computer worker", at the end, we all have the same degree.

As part of an order in my english school class, we need to write an application letter on english for a fictitious job offer. So I need to translate my degree "Informatiker". When I search for "Informatiker" on the german Wikipedia (http://de.wikipedia.org/wiki/Informatiker), and switch then the language to english, the article about the computer scientist will be displayed. But my english teacher marked it as wrong, because of the reasons said above.

I agree to write the exact role like application engineer if you currently working as such one. But in my case, I'm not an application engineer. I'm a general IT-specialist | computer sientist.

If you have a particular degree in CS, you say just that, "I have a Bachelor in CS", "I have a Master's in CS", "I have a PhD in CS".

If you are an "Informatiker EFZ", an apprenticeship that does not so much as exist outside of Switzerland, then that is your actual qualification and that is the exact term you should be using in English as well. Everything else is misleading. "Computer scientist" is plain wrong because you lack a degree in CS, and "IT specialist" is useless as it has no real meaning, different readers will understand it very differently.

So what you should ideally be writing is

Informatiker EFZ (qualified IT specialist)

Just like in German, really, where I'd write "Informatiker EFZ (Fachinformatiker)". "Informatiker" alone does not suffice as it's a one-size-fits-all generic word, "Fachinformatiker" alone is misleading because you're actually an Informatiker EFZ, and "Informatiker EFZ" by itself is insufficient as no German will know what the heck that even means.

There are many, many words for this. For starters, it may look to somebody on the outside that everybody who "does something with computers" is doing the same kind of job.

This is as true as saying that everybody who has to do with publishing written words is a "writer", whether they write content (fiction or non-fiction), news articles or research papers. Whether they make paper, design printing presses or run a publishing house. Or edit texts.

In the same way, when it comes to computers, you have designers, architects, programmers, developers, system analysts, testers, system administrators, network specialists, ... The list is nearly endless.

It is hard to come up with any word that would cover the jobs from high-level strategic software architect to first line help desk employee, from programmer to requirements specifier or from embedded systems developer to IC-designer.

What is important is to realize that there are many names for academic grades, and it is usually seen as highly inappropriate to use those unless the person has actually fulfilled the academic requirements to deserve such a title.

Although scientist is not a "protected" title, it is usually reserved for people who work in academia. Most people in IT-related jobs do not. Engineer is a protected academic title, at least in some countries.

Someone who works scientifically in computer-science is unlikely to call themselves a computer-scientist, unless they want to keep their job description vague (because their audience would not understand the distinctions anyway).

IT-specialist sound nice, but it implies that somebody is specialised. And the IT-field is so incredibly wide, that being a specialist in it means very little. It's like being a language-specialist.

The simplest, all encompassing word for a professional in the IT-sector would be IT-professional. It means they do "something" with IT, and they make a living out of it.

When it comes to the technical part of creating software, words like programmer, developer, software engineer are used. What they mean exactly depends almost entirely on context. For example, I am by the laws of my country certainly no engineer, but somehow my current employer has designated me as a software engineer. What's in a name :)

IT is not computer science.

Your teacher is quite correct, though there's no such thing as "Computer scientists ()who are academic IT specialists."

information technology in·for·ma·tion tech·nol·o·gy
noun: IT; plural noun: ITs
1. the study or use of systems (especially computers and telecommunications) for storing, retrieving, and sending information.

Note especially in the definition. IT is essentially about information, its related systems and applications, not necessarily about computers at all. (Though in practice, it may turn out that there can be no IT without computers.)

On the other hand,

computer science com·put·er sci·ence
noun
1. the study of the principles and use of computers.

Computer science is essentially theoretical in nature dealing with the principles of computers and to an extent, their eventual use. It does not deal with the study, design, development and organization of Information other than from a computer science perspective.

HTH.

[meta] This, as the OP already noted, is a question for SO, not ELU.