It is best to talk to your local recruiter for the most recent policies - but, most military branches have a 'delayed entry' program. This program allows you to sign up when you turn 18 (or in some cases when you are 17 with parents consent) but you don’t leave for basic training until a predetermined date after you graduate from High School. Note - most branches are very competitive these days and will not accept enlistees without a High School diploma. While in the delayed entry program you are required to check in with your recruiter regularly, and there may be events that you must attend to remain in good standing. Good luck and thank you for considering serving your country!
I do not believe they will. You need to contact a local military recruiter in your town (Army, Navy, Air Force, Marines, and Coast Guard). You could also talk to a high school ROTC department and your high school counselor.. Good luck and I appreciate your desire to serve your country in the military. You could also inquire about attending the military academies (West Point, Annapolis, Colorado Springs, and the Coast Guard Academy). Fantastic education and graduates enter the military as officers upon graduation. I am a West Point graduate and was a pilot in the U.S. Air Force. Please contact me if you need additional information.
It really all comes down the the Branch you select and in what capacity you are asking. To my knowledge you can sign up for the military after your Junior year is complete (on the condition you graduate the following year).
I am a Marine and I was in the Delayed Entry Program(DEP) before my Senior year started. During my time in the DEP, we were called poolees. I am not sure of the full obligations of the program but I would go to the Recruiters office a few times a month (on the weekends). I would help the recruiters with the other poolees. Once a month we would run a mock Physical Fitness Test (PFT). This was to help us improve and be better ready for Boot Camp.
On a side note, my nephew served in the Army. I believe he was able to go to boot camp before his Senior year. After completing his Senior year, he went to Military Occupational Specialty (MOS) training. Later after MOS school, he joined his unit and continued his military service.
I do not know the full details of all of the services. Sorry I do not have any more information. I hope this helps.
Thomas recommends the following next steps:
Each service has different rules and programs. Some allow a High School student to commit while a Senior in HS (if under 18 need parental consent). You should contact your local recruiter for current information.