My Grandson Just Started All Day Kindergarten This Year. He's

My grandson just started all day kindergarten this year. He's been having some behavior problems that usually occur at the end of the day. He is a very active child and also at times doesn't listen well. He does demonstrate some attention seeking behavior like writing on the walls or making some kind of mess. My daughter-in-law will be having a parent teacher conference this week to discuss his behavior. I babysit for him once a week and noticed he has a lot of the same symptoms that my youngest son had and I feel he might have ADHD. What kind of symptoms indicate ADHD?