“By this time, B’H the young person had about 15 years of Jewish schooling. Should we expect that they are able to fortify themselves by this time (I presume parents, friends and community did not abandon them)?”
Extremely foolish comment for multiple reasons. To take one, Yochanon Kohen Godol was the tzadik and Kohen Godol for 80 years when he became an apikorus tzeduki.
But he was fortified, you say!