I tried that long ago in high school. Dead car battery, replaced the acid with new acid...still dead car battery.
I guess they’ll tried that yet...but they’ll learn.
I’ve also tried that.
I took a fully charged battery, dumped the electrolyte. Took freshly purchased, properly mixed electrolyte and poured to proper level in each cell.
The battery was stone dead. It would not take a charge.
I did this as an experiment to see if regular electrolyte changes would increase battery life, considering new electrolyte is so cheap.
Lead sulfate covers one set of plates in a dead battery, a coating which hardens with time. Some commercial chargers blast higher voltage at low amps through the battery to fracture the hard crust and initiate a charge. If successful, most of the sulfur dissolves and once more forms diluted sulfuric acid electrolyte.
A charged starter battery always has dense electrolyte with a specific gravity about one-quarter higher than water. Dead battery has dilute acidic water left inside, which freezes more easily.