I appreciate the counsel in GHB 11.4: Each young woman counsels with her parents and the bishop to decide what will best help her continue to strengthen her faith in Jesus Christ.. This aligns with the emphasis given on having our youth be in charge of their own salvation, and reminds me that instead of it being the leaders (or even parents) who are always deciding these things, it is best to have the youth at the center of the decision-making process.
And to the O.P. question, I believe that Adult SS class attendance would usually be linked to RS/EQ attendance, but as the youth counsels with parents and the bishop, there may be situations where a mixed attendance pattern for a time, might be best for unique cases.