Looking on the internet deeply has found these results:

in a college is the most popular phrase on the web.

at a college 137,400,000 results on the web	in a college 147,100,000 results on the web More popular!
Some examples and use cases from the internet:	Some examples and use cases from the internet:
I work at a college as a janitor even though I'm smarter than most of the people there. I mean, you two are arguing about status at a college that correspondence schools make fun of. And I have this gig at a college upstate tonight. Right, but it still doesn't explain how a ghost ended up at a college in another zip code. I see my sister about to lap me at a college that I would never be able to get into. Look... we set up command at a college two miles east of here. But there was a brief period where I worked at a college nearby. You're in town looking at a college?	I mean, I can see you in a college or doing psychotherapy, but not at some horrible crime scene, deep in blood and guts. Boys that age would better stay in a college. In fact, I do not believe that it is conceivable in a college of Heads of State or Government, to refuse or deny each government the opportunity to set out the position of their country on a constitutional treaty. A doctor works in a hospital, just as a professor works in a college. A misdemeanor shoving match in a college bar. They're random people you meet in a college dorm. It's Like We're All In One Of Them Big Clubs You Get In A College. Look at Chandler's son: he's in a college and perfectly OK.

at a college

137,400,000 results on the web

in a college

147,100,000 results on the web

More popular!

I work at a college as a janitor even though I'm smarter than most of the people there.
I mean, you two are arguing about status at a college that correspondence schools make fun of.
And I have this gig at a college upstate tonight.
Right, but it still doesn't explain how a ghost ended up at a college in another zip code.
I see my sister about to lap me at a college that I would never be able to get into.
Look... we set up command at a college two miles east of here.
But there was a brief period where I worked at a college nearby.
You're in town looking at a college?

I mean, I can see you in a college or doing psychotherapy, but not at some horrible crime scene, deep in blood and guts.
Boys that age would better stay in a college.
In fact, I do not believe that it is conceivable in a college of Heads of State or Government, to refuse or deny each government the opportunity to set out the position of their country on a constitutional treaty.
A doctor works in a hospital, just as a professor works in a college.
A misdemeanor shoving match in a college bar.
They're random people you meet in a college dorm.
It's Like We're All In One Of Them Big Clubs You Get In A College.
Look at Chandler's son: he's in a college and perfectly OK.