If you need to assign a classroom to multiple students at once follow the steps below.
STEP 1: Login
STEP 2: Click on Students menu (icon) from the left hand side bar
STEP 3: Select the students you want to assign the classroom to by clicking on the checkbox next to the name (or filter students by status using the colour tabs on top)
STEP 4: Click on the batch action option and select "Update classroom" option
STEP 5: Select the classroom you want the students to go in
STEP 6: Click Save