The rent report cards are out. But luckily, the REITs'  parents don’t have to sign them, because they mightn't like what they see: Many of the major apartment REITs are missing out on the booming effective-rent growth taking place among Class C assets, according to October 2012 data from Dallas-based research firm Axiometrics.

While most REITs remain heavily invested in Class A properties, with 47 percent being rated at B+ or higher on Axiometrics’ A++ to C- 10-point grading scale, the research shows that many firms  are overlooking the rent growth of lower-rated asset classes.

In October, Class C annual effective-rent growth was at 3.9 percent, while Class A and Class B came in at 3.7 percent and 3.6 percent, respectively. While that's not a huge disparity, rents among varying asset classes are moving in different directions.

“The downside for the REITs is that the lower-tier asset classes have achieved some of the strongest effective-rent and occupancy growth rates over the past year," reports Axiometrics. "Then again, the REITs just announced average annual revenue growth of 5.7 percent for 3Q12, so they're still doing OK.”

So it’s not a major blow, but it could be indicative of a new trend of a shift in portfolios toward overlooked assets. Perhaps lower asset classes are not in your wheelhouse now, but there are companies making money on them.

For a full breakdown, check out the table here to see how each REIT was graded in October, by individual asset class, for effective-rent growth, compared with all other properties in their metro statistical areas (MSAs).  

AEC = Associated Estates, Richmond Heights, Ohio

AIV = Aimco, Denver

AVB = AvalonBay, Arlington, Va.

BRE = BRE Properties, San Francisco

CLP = Colonial Properties Trust, Birmingham, Ala.

CPT = Camden Property Trust, Houston

EQR = Equity Residential, Chicago

ESS = Essex Property Trust, Palo Alto, Calif.

HME = Home Properties, Rochester, N.Y.

MAA = Mid America Apartments, Memphis, Tenn.

PPS = Post Properties, Atlanta

UDR = UDR, Highlands Ranch, Colo.

The verdict? Overall, the REITs outperformed all other properties in the MSAs, but money might have been left on the table in the lower asset classes. If you're cashing in on Class C properties, leave a comment below and tell your peers why your strategy is paying off.