“How can one spot depression in children?”

Childhood symptoms of depression involve isolating, low motivation, and grades dropping. Since child and adolescent suicide is on the rise and if you have any inkling that your child may be struggling with sadness or depression, make an appointment with a therapist as soon as possible. In the meantime, try talking to the school counselor to check in on your child; these professionals can often offer the best solutions after meeting your individual child and knowing the resources in your community.

Irritability isolation crying insomnia ...

Hello and thank you for your question. Before jumping to a diagnosis I believe there are some other things to consider. I suggest having his vision and hearing checked. These are sometimes barriers to learning that are not considered. Once that is cleared, I would speak with his teachers and school counselor, who may be a social worker or an educator. Share your concerns regarding your son and request an evaluation by the school psychologist. He may require modifications or accommodations. Being a pre-teen and having a lot of hormonal changes could also play a role in how he is thinking, feeling and acting. Also, make an appointment with the pediatrician and discuss your concerns with them. They can provide you with resources and referrals for counseling should he find it beneficial. I wish you the best outcomes.
Warmest Regards,

The symptoms are those you already see. I would recommend trying to get him to see a child psychiatrist who can help with meds and talk therapy.

Low energy, poor performance, isolation, no friends, poor sleep, change in weight, feelings of hopelessness and helplessness,

Loss of interest and sad mood that affect his ability to function. Change in sleep and appetite. Let him talk to a counselor. 

If your child is reporting feeling depressed, it is important to have him evaluated by a child psychiatrist if there are problems with the following:

-Academic failure and school avoidance
-Relationship dysfunction with family, peers, and teachers
-Social withdrawal
-Negative beliefs about self or intent of other
-Seeking reassurance excessively