It is hard it watch your child struggle. I know, I have had two children who struggled at school and I was a struggling student as well. Parents want to help. There are many ways to support students by building up executive function skills. Here is a list of what you can do at home.
Accept and love: You child is who she is. Accept her; all of her. Strengths and weaknesses. Make sure she feels loved and accepted. Even when she drives you nuts.
Use timing devices: Time management is a struggle for many people. Loads of people with ADHD and other learning disabilities have even more trouble with time. Cover your house in analog clocks (the ones with faces) and teach them to tell time. Talk about time and planning often. Use timers (I like Time Timers), alarms, music playlist that you create for a specific length of time and anything else you can think of to either remind your child to do something or to remind him to stop doing something.
Clear heads think better: Take the stress off your child/teens pre-frontal cortex so it can do other activities like learning, thinking, writing and reading! Teach your child/teen to write stuff down. Use sticky notes on the inside of the front door for reminders. Write directly on mirrors with dry erase markers for reminders or positive notes. Teach your child to use checklists. Be a good role model by doing the same.
Play games: It allows you to have great family time but games also increase focus, flexibility, sustained attention and memory. My twins are 19 and my son is almost 15 and we still play games together.
Boost her up: Give immediate positive feedback when she is doing something good. My daughter is empathic, hardworking and determined. Those are great attributes that need to be noticed and appreciated as much as or more than good grades and being athletic. The good grades may get her into college but being empathic make her a good person.
Motivation him: Some children/teens need a reward at the end (goal-directed persistence which is an executive function skill as well). Keep him motivated by changing the reward often. Think win-win here. For younger children, staying up late may be a good reward (I like non-material rewards) but for teens, it is autonomy that they want so a reward may be some kind of freedom that they want and you need proof they are ready before giving it to them for their own safety.
Tough love: Being firm and consistent is important for children/teens to learn boundaries. I know it can be hard. No one wants their kid to be unhappy or mad at them but you are a parent, not a friend. Being firm helps him to learn not just your boundaries but societies. It also helps him develop his own. Be certain that he knows and understands your expectations. Many children and teens with ADHD have issue with both receptive and expressive language skills. Tell him, write it down for him, show him if needed and have him tell you what the expectations are in his own words.
Team member: Communicate proactively with teachers and other adults in your child/teen’s life. Make sure you all have the same language and expectations for her and that she is aware of that fact.
Did I mention to love him? Do that the most!