To
@Braveheart81's point, that only considers organised sport. If you look at sports participation more holistically, you see that number reduced to ~25% (2022).
View attachment 21417
Sports participation rates have maintained reasonably stable among kids over the years (unable to locate a graph which shows this unfortunately, but the raw data is available), and has actually increased very significantly since 2001 when considering all age groups.
View attachment 21418
If you're interested, AusPlay (where I've pulled these from) have a substantial number of reports and raw data available.
Edit: Worth noting as well that participation in the 'Child' demographic is substantially dragged down by the 0-4 age group (~50%), with all other age groups sitting ~85%