<i>I'm generally against mandatory subjects in education as it tends not to reflect the vast differences in experience and background, motivation and ability of the students.</i><p>At a higher education level (say College on up) I would be strongly inclined to agree with you.  Give the students freedom and they will make the right choices for themselves, and they will be the only ones to live with it if they don't.<p>At the basic education level (high school and below), this is precisely when society is teaching its children what it needs to continue its culture.<p>Most students at this age do not have the knowledge they need to make informed decisions about what they should learn, and moreover society has a vested interest in ensuring that its young people meet certain minimums.  My argument is that a second language should be one of those minimums, but that the choice of which language should be given (within resource limits) to the student or their family.<p>To answer your direct questions though, someone who cannot use a first language to any reasonable degree either has a learning disability or has been failed by the education system.  In that second case, the education system has failed them and should take extraordinary measures to correct that without lowering the standards (my argument is that a second language should be part of those standards).  And for people who are already fluent in a second language, they have already exceeded that requirement.