It's a common phrase used to indicate the presence of something in a classroom. It's often used with a noun to specify what's in the classroom, like:
* Hay un escritorio en la clase. (There is a desk in the classroom.)
* Hay muchos estudiantes en la clase. (There are many students in the classroom.)
* Hay una pizarra en la clase. (There is a blackboard in the classroom.)
It's important to note that "hay" is the third-person singular form of the verb "haber," which means "there is/there are" in Spanish.