But that easy flow - the informal level of discourse acceptable in personal communications - doesn't cut it in Harsh's class. There's a time and place to throw slang out the window.
He requires students to do quite a bit of writing - even in his public speaking classes.
Using shorthand - letters for words - won't work in college assignments or business communications.
There's a difference in the level of discourse, said Harsh. He's found that students quickly learn appropriate forms of communication in order to be understood.
"What's up?" is a greeting
Vanessa Santiago, 14, a South Hagerstown High School freshman, uses instead of saying "hello" to her friends.
"Chillin'," is a likely response that means that her friend isn't really doing anything.
She talks online rarely.
"You don't have the same communication as on the phone or in person," she said.
Her drama class classmate, 14-year-old Sarah Miller, likes to write and keeps an online diary. She's comfortable talking to friends online.
So is Chris Bell, 15, a South High freshman, who moved from Georgia about a year ago. Although he talks to his friends on the phone, he spends a lot of time exchanging messages with them online.
Communicating online is "more free," he said.
Vanessa, Sarah and Chris are in Kathy Thornhill's drama class, a class in which communication is almost all low-key and informal. However in written assignments, students need to get rid of slang, she said.
Seniors in Thornhill's advanced placement literature class write two essays per week analyzing literature.
Colloquial was a recent vocabulary word in the class. It means everyday language, explained Laura Walling, 17.
Thornhill cited a recent example of colloquial language slipping into a student's essay. In a discussion of Tennessee Williams' "The Glass Menagerie," the student wrote that Amanda Wingfield was "on his back all the time" to describe her nagging of her son, Tom.
That wasn't acceptable.
"Everything is on the formal level," Thornhill said of her students' writing.
Nick Mertz, 17, sometimes catches slang or colloquial language in his essays and realizes he's got to fix that.
Seventeen-year-old Nicole Garber finds talking online easier than talking on the telephone. She also likes to write letters, saying there's more feeling in them.
But she never would use IM (instant messaging) symbols in class assignments.
"ITI - impossible to incorporate," joked Adam Hockensmith, 17, coming up with the acronym OTS (on the spot).
He and his fellow students draw a fine line, he said.
Communicating at appropriate levels of discourse is never really a problem.