depends on what you mean by "Army". I you mean "Active Duty" Army, then no.
When you sign your ROTC Contract (I think as a 4 Yr. scholarship winner you do that during ROTC Orientation just before school starts), you are in the "Reserve Component" of the Army. You don't get any active duty military benefits because you are not in the Active Duty Army. When you commission four years later (you said you were starting as a 4 yr. HS Scholarship awardee) into the Reserve Component, there is a good possiblity you will earn the right to be
Assigned by the Reserve Component into
Extended Active Duty. A 4 Yr. HS Scholarship awardee may freely leave the Reserve Component of the Army any time up until the first day of his/her sophomore year in college, without any obligation. The details of this are in the
Contract I link to below. Starting that 1st day of Sophomore year, should a 3 or 4 yr scholarship awardee leave ROTC (either voluntarily or because of the Cadre separate the Cadet), the cadet is obligated to pay back all tuition/fees/books/stipend they have received up to that point. All recent reports of ROTC cadets/mids leaving ROTC result in a pay-back obligation, not an active duty service obligation. This is because all three branches of the Armed Forces are in draw down mode... they need money more than bodies at this point in time.
So, bottom line, when you contract, you are IN the
Reserve Component of the United States Army. "In" means you have a contractual obligation to fulfill.
Here is a sample of the Contract you will sign. Most Scholarship Awardees do not ever see or think about this piece of paper until they are sitting in ROTC Orientation at school. It is better for you to understand this contract before you arrive at school, to get your thinking straight about what you are committing to.
http://www.missouristate.edu/assets/milsci/DA597_3_Scholarship_Cadet_Contract.pdf
If you read that Contract carefully, and notice the exact wording, in four years you will Commission into the Reserve Component of the United States Army, with an eight year obligation to serve in this Reserve Component. Reading further down, you will see that you may apply for Extended Active Duty service in the Army (which is currently a 4 year obligation -- Navy is 5, by the way). This doesn't mean you are no longer in the Army Reserves. It means the Army Reserves have assigned you into the Active Duty Army. I don't know where it is in this contract, but upon completion of 4 years Active Duty, you may join the Individual Ready Reserve (IRR) for the balance (last 4 years) of your 8 year service obligation, or stay in Active Duty, with approval, beyond the 4 year initial obligation. IRR is different from the normal
Ready Reserve. IRR is the subsection of Army Ready Reserve that is rarely, if ever, called into active duty, and is last in line, behind Army Ready Reserve, to be called out of Reserve status into Active Duty status. A description of IRR is found here:
http://en.wikipedia.org/wiki/Individual_Ready_Reserve
So, to sum it up, ROTC Scholarship winners such as yourself are part of the Reserve Component of the United States Army the day they sign their Contract. Upon commissioning, usually after Senior Year also called MSIV year, about 65% (currently) of Reserve Officers will be
Assigned by the Reserve Component of the Army for
Extended Active Duty Service in the Army for four years, followed by four years of IRR assignment.
So, although both ROTC and the Academies commission cadets as Army Second Lieutenants, ROTC does so into the Reserve Component (with possible Assignment into Extended Active Duty), while West Point commissions cadets directly and only into the Active Duty Component of the US Army. ROTC in this sense has a great deal more potential flexibility and choice available to its cadets. I say potential because some ROTC cadets do not score high enough amongst their peers (OML) to qualify for Extended Active Duty Assignment.
So then, an ROTC cadet has two basic potential paths upon commissioning as an Officer in the Reserve Component of the US Army:
1) Serve 8 years as an Army Reserve -or- Army National Guard Officer
2) Petition for an get Assigned into the Active Duty Army for 4 years, followed by 4 years in Individual Ready Reserve (IRR)