I would speak to the Principal now regarding the lack of communication, letting them know you need to know in advance when the workshop is scheduled so you can take leave and organise childcare. Also let them know you are anxious about your results going along the line of ' I haven't go them back so does this mean I have failed"?
You can come across as concerned saying you really want to pass the course etc but cannot just drop everything at the last minute as I imagine others are probably in the same situation

Then when you finished, passed and got your certificate then complain.