There are potentially harmful chemicals and compounds in welding fume.  Mn in Stainless and carbons steel fume.  Hex Cr in SS fume.  There is also silica from grinding dust.  It is possible to inhale harmful quantities but if you keep your head out of the plume you may be OK.  The only way to know is to have a hygienist test your exposure.  This is a good discussion topic with your teacher.  I'm surprised it wasn't covered in welding safety.

WELCOME TO THE AWS WELDING FORUM!!

You can never go wrong wearing a GOOD dust mask.

Better yet is a low profile with filters drawing air from behind you.  The filters come in all ranges and can be added according to hazard levels of fumes coming from the welding.  Different bronze alloys can be bad.  So can many other filler/base metal combinations.

One of the best in my opinion is a helmet with 'positive pressure' air supply.  Comes through a battery pack and filter system, again off your backside, and with the air being blown in around your face keeps the fumes away and provides clean air to breathe. 

He Is In Control, Have a Great Day,  Brent