If you go to court - as a victim, a witness or a suspect it will either be a Youth Court, a Magistrates Court or the Crown Court.
If the defendant is under 18 they will most likely appear at Youth Court, unless they are charged with murder or manslaughter (which will always be at Crown Court) or a very serious offence such as robbery (which is likely to be held at Crown Court) or if they are charged with an adult (which would be heard at adult Magistrates or Crown Court).
Most criminal cases are tried in magistrates courts. If the case is very serious, or if the person on trial has requested a trial by jury it will be sent to Crown Court.