6yo dd is undiagnosed, so I can't say what the underlying 'condition'' is for certain. She has some of the ASD traits and some ADHD traits (attention deficit, not so much hyperactivity/ impulsivity, and she can become hyperfocused too).
But I can say, without doubt, that she definitely masks at school. So much so, that the effort of doing it burned her out so badly that she was unable to get dressed or attend school for 6 weeks after Christmas. She is meeting expectations academically, and is described as an intelligent and articulate little girl.
ADHD in many girls in particular does not present as 'obviously' as it does in many boys. My daughter talks about how she doesn't hear instructions in class because she is distracted, thinking about/ looking at/ listening to other things. So when she has to complete a task, she will ask a friend what to do, or copy them, because she's not heard the teacher. Imagine that churned up feeling, knowing you've missed the crucial instruction and wondering how the fuck you'll cover it/ get out of it.
i asked her why she doesn't ask her teacher or a TA. Her response was "because I know they'll say I should have been listening". Her handwriting is messy. So she comes home, locks herself in her bedroom playing 'schools' and practices 'getting it right'. She's very skilled, very adept at developing coping mechanisms, but they only work for a while and come with huge impact tonher mental health.
Kids with ADHD have problems with their executive function. Many develop very neat little tricks and work arounds to cover their deficiencies, but occasionally that mask slips, they get 'found out' and it causes great anxiety.
Our understanding of neurodivergence is changing all the time. ASD, ADHD, PDA, OCD, SPD are all variations of a theme, often coinciding at the same time (my daughter also has sensory processing difficulties when highly anxious). I think it's a matter of time before they do away with separate diagnoses and instead do individual 'neurodivergence' profiles.
We are seeking a diagnosis, because I believe it will better equip us, and her, and her teachers etc, to understand herself better and develop the strategies to help her cope better with life in the long run. Unmet needs lead to feelings of failure and mental health breakdown. Our daughter deserves better. So do other people's.