Most candidates who leave OCS are not summarily dropped from the program. You start out on the lowest of three gradually more restricting levels of probation.
The first of which is Platoon Probation: a number of candidates will find themselves on platoon probation for failing a test or two, or failing a physical test (any course, dropped out of runs, SULE I etc.). You'll be counseled by your platoon commander and sent on your merry way with an admonishment to not fail anything else. LOTS of candidates in your platoon will be on platoon probation before OCS is over. The point is not to freak out if this happens to you. Just make sure you don't get sent up to the next highest level of probation...that's right:
Company Probation. This is where you go with a history of sub par performance in any number of events. This is more serious and you don't want this. Start to worry and wire your $hit tight if you get here. You will be restricted to base for libo for the duration of OCS and will have to meet your company commander. He will also counsel you on your continued sub par performance and tell you that if you dick up more your will see the Colonel. If you fail again:
Battalion Probation: You are under serious review to be sent home. The Colonel is the only memeber of the staff at OCS who can make the call to send you home. He will look over your CRB (candidate record book, a book that documents EVERYTHING you've done at OCS), judge your bearing and desire to be an officer of Marines based on the recommendation of your staff and company commander and his impression of you, and make the call. People do come back from battalion probation with one last warning, but alot of candidates who get pulled out class to meet the Colonel never come back. As in, when you get back to the squadbay their rack is bare and foot and wall lockers are empty. If you find yourself on battalion probation your libo is restricted to Brown Field for the duration of OCS.
There is one way that will get you summarily dismissed from training: integrity violation. There is no return from this. People in your company will make this mistake.
So as you can see, you have fair warning before you are sent home from OCS. Attrition there for perfomance is really nothing to fear, but to be prepared for.
Also, for those looking for hard numbers on attrition: It varies between the type class. OCC companies have alot higher attrition rates than Golf and Echo companies. This is due to the latter having prior experience with the training environment. So to answer your question, I graduated from Echo and we lost about 22% of my platoon.
Semper Fi, Doc
