Is adhd-symptoms always visible in children?

Usually: In most cases there is some evidence of attention and/or hyperactivity by high scool or before. In rare cases someone may be able to make it to graduate school or a job that requires extensive concentration before the symptoms manifest themselves.

Not necessarily: Attention deficit disorder without hyperactivity can be silent for ears in a bright and curious child; the curiosity acts like a stimulant to engage attention. Later in life, with less structure, symptoms of add become apparent: e.g., disorganization, procrastination, forgetfulness, spacing off, daydreaming may be subtle but present if searched for. Adult add is real. Get it checked out.

Inattentiveness: 75% of children with ADHD have an inattentive form, without hyperactivity. As a result the inattentiveness may not be recognized as ADD. children who are hyperactive, especially boys are more likely to be diagnosed as having ADHD