...aaaand, breathe.
I think Sherrard was exploring the principles involved without personalising the situation?
Year 11 is a busy and pressured time, and a student may want / need to remain after school for extra lessons as exams hail into view. In addition, their exams can start as early as April, and they may finish attending school in May or whenever their exams end ('study leave')
So as well as the responsibility being a bit much, I would see the commitment as being potentially detrimental to the older kid.