Age limits are one of those great controlling levels Government loves to set, not least New Labour who loves any kind of nanny-state control more than most. Recently boosting up the age at which someone can buy cigarettes to eighteen (although not the age of consent from 16, meaning once you've had sex at that age you presumably just roll over to fall asleep...)
The more serious point is that of education, where New Labour are once again in a glorified mess, typified by having no actual Department for Education. Their desire to have 50% of school-leavers going to Uni was based on picking a figure from the air; reality has shown massive drop-out rates and students lumbered with a "mortgage on learning" around their necks if they do graduate. My memory from high school is very clear - at 16 I knew that it was sensible to have a 'fork in the road' at that age, not least because so many age limits are placed at sixteen - marriage, joining the army, tax on income. Of course moving the age at which someone stays as school to eighteen is a massive error - it forces people for whom formal education is already unsuitable into endless months of activity pushing them further away from the life they would prefer to lead. This eagerness to micro-manage our lives is typical of New Labour; they would rather force all citizens into school, uni, and work, rather than allow people to go out to see the real world.
It is crazy enough that a 16 year old is mature enough, in the eyes of the state, to have consensual sexual intercourse but not enough to walk into a polling station to vote on the parties allowing their wage to be taxed. It is deeply "unjoined" government to ask 16 year olds to stay on at school until they are 18 and then allow them the vote - what would run through your mind but "Now I can punish the party which stuck me here for so long".
There exists enough vocational courses post-16 to allow those who have done with school to continue with education. New Labour have once again chased targets rather than followed sensible policy. If the State wants to give some sense of maturity and adult status to people when they turn 16, something with which I agree should happen, then the only change to be made is giving them the right to vote.
Moving up the school leaving age is social engineering gone mental, and should be stopped.