Class Action: What to do when your child suffers a crisis in academics
Until recently, my son has always been a confident student who gets reasonable grades. But now his grades have fallen and he has started to describe himself as "useless". How can I help?

It is sad that your child is going through some difficulties. No child should ever describe himself as "useless".
It is not uncommon for students to experience a setback in their studies. This may happen after an absence from school or when they transition from one level of learning to the next.
Often, there is a relatively simple solution to the academic problem, but the psychological effects need to be handled carefully.
Your first step is to identify the root cause. Is it related to a specific subject? Can your son identify where the issues are? His initial reaction may be to issue a blanket "I can't do it" statement, but you need to move past this reaction and look at his grades systematically.
Get a sheet of paper and divide it into columns - one for each subject. In each column, list the topics which have been covered. Use different coloured pens to mark them in the following categories: "understand completely", "understand but might need to revise" and "not sure about this".
You have two aims here: to pinpoint his weak areas but also to highlight ones where he is succeeding.