Q:

Is using an apostrophe for omission more correct than not?

I recently submitted my product design coursework to my teacher, for them to check that everything was okay. And besides from the few spelling mistakes that I'd made, the only other thing I was told to do was to change all of the contractions to being two separate words.
This meant going through and changing all of the "it's"s to "it is", the "we're"s to "we are" and so on. This was because, and I quote, "The exam board see it as more correct to not use things such as contractions."
So is this really the case, is it more correct not to use an apostrophe for omission? Or is this just a miss understanding between my teacher and the exam board?
Personally I'd have though it to be the other way around, as in French it is grammatically incorrect to say "ce est" or "que elle". These should instead be written as "c'est" and "qu'elle" respectively.
Any thought on the matter would be appreciated.

A:

I agree with Jim's comment that style guides generally discourage contraction. The way I suggest you tackle it is to think of it in terms of an author's authority.
In most "formal" settings - e.g., academia, professional writing, etc. - the author does not have full control over style or "form." An editor, a teacher, or simply the general rules governing the field dictate how to handle contractions. Unless specifically permitted, it is safer not to use contractions.
In most informal settings, such as a blog post, it's up to you (and here up to me) to make that call.  
The French case is deceptive in this regard. You are right that "ce est" is plainly incorrect. Yet, in any formal setting, "c'est" is not used. You may have to use "ceci est", "cela est", or "ce qui est" in order to avoid the contraction. In English, it is less complicated in my opinion.  

