This is a common misconception but is a great question. The short answer is: you are only committing to serve an additional 3-year ADSO; then you get to make a choice. The Graduate School option is just that, an OPTION, or the guaranteed RIGHT to go to graduate school. By securing this option you can make the decision to stay in the Army and go to graduate school or leave the Army and pursue other things.
You are only agreeing to serve the additional 3 year CSP ADSO on active duty. Instead of serving 3, 4 or 5 years on active duty (depending on source of commission) and the remainder in the reserves, you will simply serve 6, 7 or 8 years on active duty. While you are serving this CSP ADSO you will command a company and be the proud owner of 100% of the Post 9/11 GI Bill for use by you or for transfer to your spouse or children.
If you choose to continue on active duty and exercise the graduate school option, you are guaranteed fully-funded graduate school at the school of your choice. Or, you can leave active duty at the end of your commissioning and CSP ADSOs.
There are many similarities between the Graduate School option and the Advanced Civil Schooling (ACS) program. For example, during graduate school under either program, you will remain on active duty as an officer. Thus, the Army will pay full tuition and fees and you will continue to receive all basic pay and entitlements. Under both programs you will typically attend graduate school after successful company command or your branch's key and developmental captain position. Further, any time you go to graduate school, through ACS or the Grad School option under the CSP, you will owe three days for every one day you spend in school. That's where the similarities stop.
There are a number of programs within the ACS program: West Point instructor, Congressional Fellows Program, Joint Chief of Staff Internship, and the graduate programs associated with individual career fields or branches like Operations Research & Systems Analysis (ORSA) or Foreign Area Officer (FAO). Selection for these programs is highly competitive and depends on your military service record, undergraduate GPA, and GRE or GMAT scores. Within each of these programs you are confined by the degree you can study and the cost of the institution. The Graduate School option under the CSP differs greatly from ACS along a number of dimensions. As long as you are selected for promotion to Captain you retain your option as a guarantee to participate in the program regardless of your undergraduate academic performance. Unlike ACS, where the Army imposes many restrictions on your program of study, institution, and the cost of tuition, the Graduate School option puts you in the driver's seat and allows you to choose both the institution and the degree. Even more, there is absolutely NO COST CAP that will limit where you go to school. There is also no utilization assignment following graduate school under the CSP Graduate School option. Following graduate school, you will return to your branch or career field to serve in the Major key and developmental positions that will prepare you for promotion in that branch or CFD.
No. When you sign the Post of Choice contract the Army agrees to send you to that post or country for your first duty assignment. You will serve at your initial post for between 24 and 48 months depending on your basic branch and follow-on professional military education (PME) course. If the Army changes your assignment, your contract will be invalidated and you will not be required to serve the additional 3-year CSP ADSO. However, if you are a participant in this program and you request a post change and the Army finds a way to accommodate your desire, you will retain the 3-year CSP ADSO.