I can add to what Michal Kalina has written that in Poland the preparation to receive this sacrament is really bad organised and that's why it's called "the sacrament of the farewell with the Church". The preparation begins in the last year of the school called gymnasium (it's the secondary school) and ends when it's finishing (not appropriate time because of important exams to High School) or in the beginning of High School (the third school) - also not appropriate, because usually people attend this school in completely different district than they live and of their previous schools. You can ask how the changing of school depends on the Church issues? Well, you prepare for the confirmation in your parish or in the parish which is the closes to gymnasium you attend. And every parish has its own rules for preparation process, and you have 2 options: finish the preparation in your previous parish or discuss with the new one.
The process of preparation consists of going after every Mass and service to priests with special index to sign that you were present and some meetings in groups (but, generally, young people, if they are not believers, make troubles during these meetings). The all stuff is really formalised and I know many people, including me, who although are practicing, couldn't receive the sacrament because of arguments with priests on formal issues and non-believers receive this sacrament, but now they don't attend Church anymore (probably some of them they appear in church again for wedding).
I was expelled from the confirmation just 4 days before the ceremony, because in the parish there were big changes (also in clergymen) and because of my Orthodox views (earlier for them it was not problem). It was really tragic for me, although I was considering conversion to Orthodoxy even before this year of preparation, but my spiritual father said I should be cofirmated in RC Church because in Orthodoxy mainly rituals attract me (of course it was not true, but the fact is that I wasn't prepared to convert in this time when I was 15). Well, generally it's long story and difficult to describe it, however my unrealized confirmation brought me into Orthodoxy
I know that before the reform of education (there used to be the first and the secondary schools) the situation was a bit better and people used to be confirmated in younger age - 1-2 year after the first Communion in the age of 7-8