I would disagree with your assessment that you should never surpise the teacher with an unplanned visit. IMO, it seems as if your visit spurred the teacher to express the negative thoughts she's had towards your son's performance in class.
Neato
Yes, thank Neato, you are correct, however, I guess in my own mind I meant that I would still communicate with her; I would just plan it with her so that we could keep moving forward in a more positive way.
I also agree I wouldn't wanted to have waited until the end of term to hear that. I had been doing my usual 'haven't heard anything, so everything must be fine' thing and should have organised more communication before now.
I thank you all for your replies, advice and encouragement.
