Commercial chalk for kids composition
I am afraid whoever told you "sulfuric acid carbon" does not know the basic terminology (must be from non-chemistry background). There is no such thing as "sulfuric acid carbon" to begin with. Any carbon obtained by charring with sulfuric acid would be jet black. Nobody would like to have a black chalk.

It is very easy to parse $\ce{CaSO4.2H2O}$ incorrectly. 

I think he/she misread the calcium $\ce{Ca}$ symbol for carbon which is $\ce{C}$. 

$\ce{SO_4^2-}$ can be easily misrepresented to be sulfuric acid.