(Graduation day at the U.S. Naval Academy, an institution with an enviable 89-percent completion rate. (Linda Davidson//THE WASHINGTON POST))

And when it comes to standards, no aspect of the academy gets closer scrutiny than its prep school. The Naval Academy Preparatory School in Newport, R.I., provides a year of academic catch-up for promising students who lack a strong educational foundation.

Critics allege the prep school is a back door for sub-standard students, many of whom, they say, don’t belong at the academy. The prep school is viewed by some as a way for academy leaders to get around their own rigorous admissions process, particularly with black and Hispanic students and athletic prospects. Academy leaders, for their part, acknowledge an institutional push for greater diversity - - although not, they say, at the expense of standards.

Some days ago, a source challenged me to investigate the recent history of retention and graduation at the preparatory school. The source had heard reports that half or more of one recent NAPS class had dropped out. A statistic like that, if true, would undermine both the overall academic currency of the academy and the push for greater diversity on the Annapolis campus.

I requested the records from the academy. They arrived a few days later. The results were not what the source had expected.

Of the 256 students who entered the preparatory school in fall 2006, 155 stayed on to graduate in spring 2011. That’s a graduation rate of 61 percent. Of the 120 minorities in that class, 74, or 62 percent, got diplomas.

The corresponding graduation rate for the 2005 prep-school class was higher, 68 percent. Of the minorities in that class, 70 percent completed their studies.

Of the 261 students who entered NAPS in fall 2007, 167 are still enrolled. That’s 64 percent retention, and it’s comparable to the success rates of the two previous years.

Of the 284 students who started in fall 2008, two-thirds (188) are still enrolled. Of those who enrolled in fall 2009, the retention rate is 76 percent.

The Naval Academy is a top-tier higher education institution; its overall graduation rate is 89 percent, according to the federal government, a figure just shy of the 90-percent mark that is the goal of the nation’s very top universities. The academy’s overall admission rate in 2010 was a ridiculously low 8 percent, more selective than Princeton.

By that standard, the retention and graduation rates of the preparatory school are strikingly low. But then, the very purpose of the prep school is to serve a group of students who have weak academic preparation and who, for that reason, are at greater risk to drop out.

National graduation rates for blacks and Hispanics are below 50 percent. Elite institutions don’t necessarily fare much better. An Education Trust report found a 69-percent graduation rate for Hispanics at the flagship University of Illinois, and a 58-percent graduation rate for blacks at the flagship University of Wisconsin.

What do you think? Is a graduation rate of 60 to 70 percent acceptable for the Naval Academy Preparatory School? Please post your thoughts in a comment.