ADHD student need structure in their life. They lacking inner structure and have problems with perception of time. Therefor they can not anticipate on things to come.
The next issues are recomended:

• offer boring and difficult tasks in the morning hours. ADHD children can concentrate better during the morning
• limit the number of change of lectures
• stick to your schedule as much as possible
• show the dayly program at a visible place (children with ADHD have problems with time perception
• prepare changes in advance
• repeat the rules, schedules and aggreements over and over again