This happened to my DD13 when she was 8. We never did really figure out why. She *loved* her teacher (and STILL writes to her at Christmas) so it wasn't that, nor were there any upsetting things we could identify. No world event, no friend moved away, no change in my work hours. One day she just called home crying that she missed me. The teacher was concerned because it was so unlike her. It was almost like the separation anxiety stage that babies go through.
I ended up going to have lunch with her a couple of times a week for a few weeks, plus made sure she got more sleep, cut back on extracurricular activities (prior to that year, we only let her do one thing, but that year she was doing drama, piano, ice skating, and horseback riding. We decided it was just too much for her), and just gave her extra attention at home.
She eventually got better, and is now a normal 13 year old who doesn't want to be seen with me at all.
It was really frustrating though, having her so upset and not really being able to do anything to help her, besides just be there and help her through it.
I ended up going to have lunch with her a couple of times a week for a few weeks, plus made sure she got more sleep, cut back on extracurricular activities (prior to that year, we only let her do one thing, but that year she was doing drama, piano, ice skating, and horseback riding. We decided it was just too much for her), and just gave her extra attention at home.
She eventually got better, and is now a normal 13 year old who doesn't want to be seen with me at all.

It was really frustrating though, having her so upset and not really being able to do anything to help her, besides just be there and help her through it.
