I don't know if the other service academies provide guidance but here is a recap of the guidance we received from West Point:
The test of provide "half the support" is in regards to monetary support, not the length of time.
The added together for us the cadet pay received (W-2) over $5000 plus the pay advance by the government to purchase issued items - over $5000. They also added together the cost of room and board supplied by the government, about $1500 plus the cost of tuition for one semester, $25,000. The IRS doesn't count the tuition as a "scholarship" so this figure must be counted as "support".
This totaled about $39,000. (I was a little off in my above post)
As parents we are allowed to include the cost of room and board, tuition (if any) books, medical, dental care and insurance for 6 months.
Of course, each family situation is different and tax opinions may vary.