Why Child Can Do It Some Days Not Others: ADHD Skills Inconsistency Explained

Understanding why child can do it some days not others begins by challenging an assumption common in homes and schoolrooms: the idea that once a young learner demonstrates a developmental skill, that ability becomes a permanent, reliable baseline every single morning.

When an adult sees a child tie their shoes, write sentences neatly, or pack a school bag on Tuesday, we expect them to reproduce that performance on Thursday. When that performance collapses into tears, refusal, or frantic running, relatives and educators often assume the child is choosing when to cooperate and when to be obstinate.

Having lived through these uneven days as an early childhood researcher holding a doctorate from Deakin University and as a parent with ADHD raising two daughters in Victoria, I know how heavy that misunderstanding feels. My own adult brain experiences the same swings: on full fuel days I can organise academic datasets and coordinate community projects, yet when sensory fatigue drains my battery, buttering toast or answering a phone call feels like wading through wet cement.

Why Child Can Do It Some Days Not Others in the Hallway

In our home, Tuesday and Thursday morning often look as though they belong to two completely different families.

On Tuesday morning, my daughter woke with energy to spare. She dressed herself down to her socks, buttered her own toast, and chatted away about the family of wattlebirds outside her bedroom window. She had her hat in her bag and her shoes on before I even picked up my car keys. As a mother, those mornings make you exhale with relief. You tell yourself that the household rhythm has finally clicked into place.

Then Thursday arrived. Same hallway. Same pair of blue runners sitting by the front door. Same time of the morning.

I handed her the shoes, and her entire posture folded. She dropped straight onto the timber floorboards, shoved the runners away, and began sobbing that her feet felt too hot, that the tongue of the shoe was hurting her ankle, and that she could not do it.

It took understanding the biological foundations of executive energy to see what was really happening. My daughter had not forgotten how to pull a velcro strap. She was not trying to make us late out of spite. Her nervous system was running on empty. She had spent Wednesday coping with loud classroom chatter, filtering overhead light buzz, sitting upright on a mat, and holding her body together. By Thursday, her sensory and cognitive battery was completely flat.

The Writing Book That Confused the Classroom

This friction is just as common at school. During preparatory year, my daughter brought home her school writing folio.

On page fourteen, dated a Tuesday morning, she had drawn a detailed echidna with dozens of fine pencil spikes. Beneath it, she had written three neat sentences about how echidnas dig for ants in the bush. Her pencil grip was steady, the letters sat neatly along the dotted thirds, and her punctuation was accurate. Her teacher had placed a proud little star at the top of the page.

On page fifteen, dated forty eight hours later, there was a single wobbly word: the. The pencil line was pressed so hard into the page that the paper had torn. The rest of the sheet was completely blank, save for a few dark scribbles in the bottom corner where she had pushed the lead until it snapped.

Reading that note made my chest ache. The teacher saw a moral refusal. What they could not see was that Thursday morning had begun with an unannounced fire drill right before reading groups. The classroom was warm and sticky from rain on the windows. The fluorescent tubes had an irritating buzz, and her best friend was home sick. Her nervous system had spent every drop of dopamine and working memory just staying seated on the mat. By the time the writing book was placed in front of her, she did not have the physical fuel left to hold a pencil.

The Myth of Linear Mastery in Early Childhood

Traditional educational benchmarks rely on a linear staircase model: a child learns a step, demonstrates proficiency, and stands permanently on that new level of independence.

In neurodivergent development, executive function is not a permanent concrete step. It is a fluctuating tide that rises and falls with physiological energy, sensory load, and chemical regulation in the brain.

Clinical research by Russell Barkley highlights that individuals with ADHD do not have a deficit of knowledge; they have an issue with the timing and transmission of that knowledge at the point of performance. The child knows what to do, but their executive system lacks the immediate metabolic resources to deliver that action on demand.

Emotional Load Versus Skill: The Electrical Grid Model

To understand why child can do it some days not others, think of skill ability as an appliance, and emotional load as the electrical current in an old weatherboard house.

A child might have a high powered blender sitting on the bench. It has sharp blades and can puree soup in thirty seconds. That is their intelligence, their vocabulary, and their conceptual understanding.

However, if the house already has an electric heater running, the washing machine spinning, and the oven baking, turning on that blender will trip the circuit breaker. The blender is not broken. It does not need to be repaired. The electrical grid simply cannot carry another demand.

When a young child walks into a preschool or classroom, their internal electrical grid is often already running at maximum capacity:

• Sensory Demands: Polished vinyl floors bounce sound like an echo chamber. Fluorescent ballasts hum continuously. Woollen uniform jumpers itch against sensitive skin. Filtering this ambient clatter consumes substantial energy, as we explore in our guide on classroom noise sensory overload.
• Social Vigilance: Children with ADHD are acutely aware that they move faster, talk louder, and get corrected far more frequently than peers. That background scanning creates a low level tension that siphons energy away from learning tasks.
• Cognitive Transitions: Shifting attention from an unfinished drawing to a structured task requires flexible set shifting. For an ADHD brain, slamming the brakes on one activity to accelerate into another feels like grinding gears, an experience we break down in our article on sensory micro transitions preschool.

The Masking Hangover: Why Thursday Pays for Tuesday

Another biological factor driving skill inconsistency is the cumulative cost of performance, often referred to as the masking hangover.

When a child expends every ounce of self control to manage a demanding social day on Tuesday, their autonomic reserves are heavily drawn down. They borrowed energy from future reserves.

On Thursday, the biological invoice arrives. The child exhibits lower tolerance for tactile irritation, decreased working memory, and heightened emotional vulnerability. Recognising these post effort cycles helps adults predict low capacity mornings and proactively reduce demands before friction erupts.

Will Not versus Cannot: Reading the True Signs

Translating Skill Inconsistency into School Accommodations

Under Australia’s early learning guidelines overseen by ACECQA, educational programmes must be responsive to each child’s individual strengths, interests, and developmental rhythms.

When sitting down with educators, we can replace defensive arguments with practical accommodations:

How We Protect and Support Our Children at Home

When the outside world misunderstands our children, home must be their sanctuary. When my daughter walks through the front door with slumped shoulders after a hard day, I do not ask her why she did not finish her workbook.

Here is how we handle low capacity moments without escalating tension:

By releasing the expectation of flat, mechanical consistency, we align ourselves with our children’s true developmental biology. We celebrate the high energy peaks without punishing the low capacity valleys, providing grounded safety through every uneven day.