We teach our kids to push themselves beyond their limits and you will see the results only to have them start their careers at the same point as the ones that just slide by...........
I agree with the Major, the reward for excellence comes with getting AD and a better shot at the cadet's branch of choice, of course some cadets that fall toward the bottom of the list still get their preferred branch, being higher on the list helps with a cadet's chances.
As it's been said, a lot of this is taken care of with attrition, those that don't put in the effort often leave the program. Being toward the bottom of the OML does not always equate to being an inferior officer, there are a lot of factors that can come into play. The cadets major, if it is extremely difficult can result in a lower GPA while grade inflation at certain colleges can help a cadets GPA, now a bad day with the standardized testing can have a big effect. A cadet may come from a highly competitive battalion, while they may find themselves at the bottom of their battalion OML they could have easily been toward the top at a different battalion. Looking through history there have been some pretty good officers that were toward or at the bottom of their class at WP, I'm sure the same goes for ROTC.
In my opinion, ROTC and even WP is just a pathway to a commission. Where you were on the OML is never discussed once the new LT arrives at BOLC, it's a start of a whole new ballgame. This is a place where they no longer have to balance school and ROTC, 100% of their effort is now on their branch training, this is where what type of an officer they will be starts to be molded.
Talking to my son over his last 4 years of AD, and looking back at my own experiences, how a person commissioned and how they ranked at ROTC, OCS, or an academy had little consequence toward how they performed as an officer.
Both my sons were decent students in high school, above 3.5 GPAs, they didn't have the highest ACT/SAT scores. An admissions counselor at one school told my younger son that he would have trouble in college because his ACT scores barely made a composite of 24. He graduated college with a 3.7 while doing well in ROTC and being very active in student government, branched Aviation. Sometimes the scores and rankings are not a true test of one's abilities, just as their position on the OML does not tell the whole story.
Of course all of this is just my opinion.