The phrase "already attending" is correct and usable in written English.
It can be used to indicate that someone is currently participating in an event or activity, often in response to a question about their attendance.
Example: "I appreciate your invitation to the conference, but I am already attending another event that day."
Alternatives: "currently enrolled" or "already participating".
Fareba was already attending college and hoped to follow her father's footsteps into the legal profession.
But in looking toward the mainland, Dr. Dobelle has hardly neglected those already attending the university.
An additional 159 students already attending Hofstra were also admitted to the college, bringing the total to 257.
As a teen-ager in tsarist Russia, Mayakovsky was already attending anarchist meetings and distributing socialist leaflets.
With the primary still a year away, he is already attending twice as many events statewide as he did in his last competitive race.
He was already attending off-campus demonstrations organised by the now-banned group al-Muhajiroun, which had railed against the military in its rhetoric.
The next elections are not due until 2012, but so grave is the impasse that politicians are already attending to their political futures rather than present troubles.
"It doesn't matter whether they're already attending or not, once they aren't living here anymore we cannot allow them to attend".
While hundreds of students intended to start using the vouchers next week, fewer than 50, from two Pensacola elementary schools, were already attending private schools under the program.
Gore is already attending a series of non-fund-raising "thank you" events around the country, and he plans to establish a political action committee this summer.
A handout circulated at the meeting instructed families to donate, qualify for a tax credit and then apply for a scholarship for their own children, many of whom were already attending the school.
