To say "our classroom" in Engpsh, you can simply say "our classroom." If you want to specify which classroom you are talking about, you can say "the classroom we are in" or "the classroom we use for [subject]." For example, you might say "Our classroom is very spacious" or "The classroom we use for math is on the second floor." You can also use possessive pronouns to refer to the classroom, such as "our classroom" or "the classroom that belongs to us."