Looking on the internet deeply has found these results:

in the class is the most popular phrase on the web.

In the classroom 147,500,000 results on the web	in the class 165,900,000 results on the web More popular!
Some examples and use cases from the internet:	Some examples and use cases from the internet:
He didn't lose his temper in the classroom. In the classroom, the children passed around... a piece of paper with the words: We had observers watch videos of teachers in the classroom and rate how they did on a range of practices. In the classroom, you are an outstanding Ranger, but in the field, you collapse. Your authority ends in the classroom. The place of a teacher is in the classroom. In the classroom, we have arguments on some of the most fiercely held moral convictions that students have about big public questions. But he seems to be holding back in the classroom.	Dawson, you are the most creative person in the class. Jack is the most intelligent boy in the class. I just... Wish that you could stay in the class. I guess that makes you the smartest girl in the class. Diana Skouris is the smartest in the class. A lot of pain and anguish in the class tonight. Booth, there are only 15 children in the class. The best grade in the class.

In the classroom

147,500,000 results on the web

in the class

165,900,000 results on the web

More popular!

He didn't lose his temper in the classroom.
In the classroom, the children passed around... a piece of paper with the words:
We had observers watch videos of teachers in the classroom and rate how they did on a range of practices.
In the classroom, you are an outstanding Ranger, but in the field, you collapse.
Your authority ends in the classroom.
The place of a teacher is in the classroom.
In the classroom, we have arguments on some of the most fiercely held moral convictions that students have about big public questions.
But he seems to be holding back in the classroom.