I don't agree with giving 16/17 year olds the vote. Some of them are level-headed, but have little experience of life. They will still be guided by their teachers.
As the school leaving age has been increased they will not be out earning their keep (generally speaking).
Just as American colonists believed in "No taxation without representation" I believe there should be no representation without taxation. (with certain caveats for those who, due to age/infirmity, are unable to work)