Correct Trang. That's the reason I opened this discussion page, because the English translation says, "How does she grade him?" This is incorrect. "Giudicare" means to judge or evaluate. If you are speaking of a teacher grading him, that is, giving him a grade, you would say, "Lei come lo valuta," or even more probable, "Che voto gli da?" (What grade does she give him?).
There are four ways of saying you in Italian: tu, voi, Lei (capitalize the first letter), and Loro (capitalize the first letter).
Tu (for one person) and voi (for two or more people) are for informal situations.
Use Lei (for one person, male or female) and its plural Loro in more formal situations to address strangers, acquaintances, older people, or people in authority.
Capitalize Lei and Loro to distinguish them from lei (she) and loro (they).
@AlexBuxton, how old are you? Students always address one another with the "tu" form. However, "Lei" is used all the time in formal situations. Switch on your tv and you'll hear it within minutes.
Loro, however, is rarely used nowadays as the plural of Lei. Sono d'accordo con te su quel punto.
This thread suggests a couple ribald jokes
It's too bad Duo got rid of the more private discussion areas associated with each account, or I'd post it there. Essentially, the idea is whether something had used "lei" in talking to you - converting the pronoun to a verb.
I think it's just a weird word order.
"Come lei giudica lo?" would be the most word-for-word translation, but then that doesn't sound very good, so you could do "Come lei lo giudica?" but I don't think you're supposed to put two pronouns next to each other like that. So it becomes "Lei come lo giudica?"
I really do believe that DL would be better to remove 'grade' as an english translation for this verb. I can't find it used in that way anywhere else where I've been and I think its confusing to use it. I can understand, I think, how it has been chosen, but I really believe it serves to confuse. Doing this is not easy in any event (or at least not for me!), so the least confusion, the better it is, I believe.