If your teacher isn't present, just have a substitute teacher take his or her place. You can briefly mention the substitute teacher. For example:
"The substitute teacher came into the classroom and yelled at everyone to get to their seats. He mentioned something about our teacher being out for some time and he was unsure whether or not he will be back."

If you have a free period, then you can use it to hang out in the library or attend other classes if you wanted to. If you're character is the only one with a free period, I want to apologize but I tried to make the schedule so that everyone could get the class they wanted. I would suggest switching your class schedule around or make a new character that doesn't have a free period at that time.

Due to time zones, there will obviously be people coming in "late." So teachers are not to mark anyone tardy unless the RPer states that their characters are late.

All classes take place on School Grounds unless your class decides to take a field trip or something. But they will most likely stay on School Grounds.

Most of the classrooms are pretty obvious-- Potions in Potions Classroom.
But I'm putting up a list of the locations of all the classes just in case you don't know where it is.

~ Art
(Art Classroom)

~ Battle Strategy/Physical Combat
(Training Grounds)

~ Potions
(Potion Classroom)

~ Free Period
(No class on this period. The library is a good place to spend the free period. Students are not allowed off campus during Free Period)

~ Archaic Sciences
(Archaic Science Lab)

~ Beastiology
(Beastiology Room)

~ English
(English Classroom)

~ History
(History Classroom)

~ Physical Education
(School Pool)

~ Cooking
(Cooking Classroom)

~ Physics
(Physics Classroom)

~ Music
(Practice/Music Rooms)