Looking on the internet deeply has found these results:

teach a class is the most popular phrase on the web.

teach in class 1487,000 results on the web	teach a class 11,090,000 results on the web More popular!
Some examples and use cases from the internet:	Some examples and use cases from the internet:
That's not my department and I have to teach a class in... I teach class in a half an hour. You can, of course, sleep in the class but I don't want to teach class in your room! This is her last night in town before she moves to Rio to teach a class in pole dancing. But I've also been asked to come into a high school where there's been a lot of trouble and teach a class in philosophy. You know, it's always been a dream of mine to teach a class in this gym. You have to teach this in class tomorrow. I have to teach a class in 15 minutes.	Both of them, they should teach a class. You know, it's always been a dream of mine to teach a class in this gym. I could teach a class on crushing it. Dr. Garner's on his way to teach a class right now... I mean, you could teach a class on bedside manner to most of the doctors around here. I teach a class and I have a lecture at Rutgers on Saturday. They've been after me for a while to teach a class. You could teach a class on how to be a good friend.

teach in class

1487,000 results on the web

teach a class

11,090,000 results on the web

More popular!

That's not my department and I have to teach a class in...
I teach class in a half an hour.
You can, of course, sleep in the class but I don't want to teach class in your room!
This is her last night in town before she moves to Rio to teach a class in pole dancing.
But I've also been asked to come into a high school where there's been a lot of trouble and teach a class in philosophy.
You know, it's always been a dream of mine to teach a class in this gym.
You have to teach this in class tomorrow.
I have to teach a class in 15 minutes.

Both of them, they should teach a class.
You know, it's always been a dream of mine to teach a class in this gym.
I could teach a class on crushing it.
Dr. Garner's on his way to teach a class right now...
I mean, you could teach a class on bedside manner to most of the doctors around here.
I teach a class and I have a lecture at Rutgers on Saturday.
They've been after me for a while to teach a class.
You could teach a class on how to be a good friend.