If you are talking about going to the Ranger School, it will depend on what branch you pick.
If you are Infantry or going into non-Infantry position coded for Ranger qualification, you should be sent to Ranger school after graduating from your basic course.
Ranger School Statistics
•60% of all Ranger School failures occur in the first 4 days (“RAP Week”): RPA, Land Nav, Footmarch, CWSA.
•30% of all Ranger School failures occur due to Personal Reasons: Admin, Lack of Motivation, Special Circumstances.
•10% of all Ranger School failures occur due to Academics: Patrols, Peers, Serious Observation Report, Medical Issues.
◦Only 2.2% of all Ranger School failures are due to Patrols (Academic).
◦Only 5% of all Ranger School failures are due to Patrols, Patrols/Peers, Patrols/Peers/Spots (Academic).
•50.13% Overall Graduation Rate last 6 years (FY 06-FY 11) 37.2% Ranger Graduates Recycle at least 1x Phase of Ranger School
•75% of those who complete RAP week will eventually pass the Darby Phase and move on to the Mountain Phase. Darby Recycle Rate is approximately 15%.
•94% of those who start the Mountain Phase will eventually pass and move on to the Florida Phase. Mountain Recycle Rate is approximately 18%.
•98% of those who start Florida Phase will eventually pass and graduate Ranger School. Florida Recycle Rate is approximately 18%.
http://www.benning.army.mil/infantry/rtb/