What is considered high myopia? What are the warning signs of vision problems in kids?

I think above 600 degrees is considered high myopia. Some warning signs would include: - complaints of not being able to see distant objects (e.g., words written on the white board in the classroom) clearly - Frequent rubbing of eyes - Excessive blinking - Tilting of head or squinting when reading or watching TV to see better - Headaches from eye strain