The phrase "a text message to a classmate" is correct and usable in written English.
You can use it when referring to a message sent via text to a fellow student or peer.
Example: "I just sent a text message to a classmate to ask about the homework assignment."
Alternatives: "a message to a peer" or "a text to a fellow student."
Less than a month before the shooting, after he had dropped out of his neuroscience program, Mr. Holmes sent a text message to a classmate that suggested he believed that he suffered from dysphoric mania, a bipolar condition that combines manic behavior and dark, depressive tendencies.
Weeks before his rampage, Mr. Holmes also sent a text message to a classmate asking about "manic dysphoria" — a psychiatric condition that combines the symptoms of mania and depression — and warning her to stay away from him because he was "bad news".
— On the day after two bombs exploded near the finish line of the Boston Marathon, Dzhokhar Tsarnaev tapped out an early-afternoon text message to a classmate at the University of Massachusetts at Dartmouth.
On Wednesday afternoon, Shayan Rostami, a 19-year-old freshman, read a text message from a classmate aloud as he walked with a group of friends to Lake Yosemite, near campus.
IT was a Monday when Benni Cinkle, a 14-year-old high school student from Anaheim Hills, Calif., received a text message from her classmate Rebecca Black saying that an unofficial fan page devoted to Ms. Cinkle had popped up on Facebook.
If you're hiding from an abusive relative or you just don't want your classmates to know how overwhelmed you feel about applying to college, a text message, even one sent in public, is safer than a phone call.
(source) Now: "to send a text message".
Even though classmates post about parties and events on Facebook, they make sure to send him a text message too, he said.
A text message from Teixeira!
