B.P.
Hi J.,
The sooner the better even if it is messey a few times. My grandson started school at age five, his first time to potty he came back in the class room, pants down around his knees and holding a wad of toilet tissue. He ask his teacher "Will someone please wipe my butt?"
He is 18 now and still gets teased. Needless to say we did not teach him soon enough. B.