Should have thought=would have thought?

Hi, dear members. I have been locked in an argument with a Chinese teacher about the use of "should have thought".
The sentence in question is seemingly from a reference book for preparation of an English test:

Aren't you tired? I should have thought you had done enough today.

I think in this case "should have thought" equals "would have thought", which indicates the speaker is surprised at another guy, who is supposed to be tired but is still vigorous, when he sees the guy is still working. The speaker expected the other guy to be tired but it turns out otherwise. It also indicates the other guy is doing the work of his own volition, not being forced.

But the Chinese teacher insist that "should have thought" means "the speaker should have thought he was tired but actually the speaker didn't", indicating the speaker regrets having been inconsiderate towards the other guy by pushing the guy to do some work although the the guy was already tired.
And he he thinks "would have thought" expresses speculation of the past or subjunctive mood, which is different from "should have thought".

But I have read many threads here and know that "should have thought" is just another way of saying "would have thought", so I disagree with him.

So who is right? Please shed light on this.

Thank you.