From Pop Matters:
Exclusively. The writing staff [of Glee] has barely been able to come up with any dialogue, let alone a storyline, for any of the non-white kids.
The characters are named Mike Chang and Tina Cohen-Chang. And, no, there is no indication that they are related to each other. Are you kidding me? High-paid Hollywood writers couldn’t come up with a second Asian surname?
There is an African-American guy in the choir. In one episode, he wasn’t there and his absence was explained because he had a spider in his ear. But it was just a convenient way to create an uneven number so that one of the white kids had to do an awkward duet with the white teacher.
The non-white character that has come closest to actually becoming a full-fledged character is Mercedes. She can sing like nobody’s business and has been given the spotlight in a few musical numbers. She even had one B-storyline when she had a crush on the gay kid. But again, it ended up that she was a foil to push him in the direction of coming out of the closet.
There was a whole episode where a teacher (Jane Lynch having too much fun as Sue Sylvester) points out that the minority students are second-class citizens in the glee club. Of course, she was doing it to try and break the group up. Did this lead to getting to know the non-white characters better? Not really. Their main complaint seemed to be that they weren’t allowed to sing enough hip-hop and R&B. Seriously.
But it was a moment from another episode that really drove home that the writing staff of Glee understands the disparity they’ve created. All the characters were picking names out of a hat to partner up on a ballad. But Tina, the Asian-American girl, says “other Asian kid”. Funny throwaway, but really?