In the context you provide – a training course – I would go with this:
- Uninformed
- Beginner
- Intermediate
- Expert
These are students and teachers who will read this. Many of the terms provided in other answers (e.g., "ignorant", "virgin") may meet the requirement for the definition, but are inappropriate in terms of context.
"Uninformed", in this particular context, strikes me as non-judgmental.
"Newcomer" is also very good (but already provided by @Sawbones).
Also, just fyi...
Many organizations actually use "Beginner" for the level where a person has no knowledge at all about the topic.
Then comes "Basic" or "Novice".
So it's common to see this:
- Beginner
- Novice (or Basic)
- Intermediate
- Expert (or Advanced)
You can find plenty of examples online. In my quick review, the one thing they all had in common was "Beginner" came first (and was synonymous with "uninformed", "newcomer", "entry level", etc).
Newbie
orNewb
. In a case where this describes the ability to perform a function,Trainee
might be appropriate. Universally, though,Novice
is IMO the best.