• object-oriented (this is their FIRST proper programming language - they don't even know how to write loops yet and you want us to teach them OOP at the same time?! And as it turns out, I had one student who literally could NOT work out how to use a loop - kept writing 20 variables for 20 iterations. i.e. her variables never varied!)
• variables are weakly-typed (use it for anything, whether it's what you first used it for or not, Python doesn't care)
• indentation has to be exact (i.e. no brackets, just exact indentation). I had one student whose program wasn't working, and it even took ME a while to find what was wrong with it (a missing space).

I think there was more, but that's what I remember off the top of my head. If it was up to me then I would've used Pascal - that's what it's designed for! But at least C# has strongly-typed variables, and doesn't care about your indentation (and unfortunately there was no non-OOP language choice available - I'm not sure how this got in the curriculum when every teacher knows you only teach one concept at a time). As I said, many other teachers felt the same way, but couldn't get it past their school admin's.