My first programming language when I started to study CS at university was SML using MoscowML (in 2001).

It seemed like both I and a lot of other students had a lot of issues with it. It seems like the university agreed as they later moved away from it.

Basic SML might not be hard to learn but you quickly have to go to concepts like recursion that is not a very easy concept to grasp for beginners. SML seems more suited for the theoretical mathematical (for lack of better words) parts of computer science rather than the more practical parts.