When doing a safety check of the school, one of the basic inspections is to verify that the exits are free from obstruction.
Full access to exit doorways.
Verify that nothing is in the way of any exits to the building. Often, especially in elementary schools, you will find bins with balls, toys, sleds, etc. stored in vestibules, or in hallways near exits to the school yard. These bins often impede in the door way. You have to make sure that the full opening to these exit doors are accessible and that no slalom has to be done in order to exit the school in case of emergency.
Doors open a full 90 degrees
Having objects behind doors can prevent them from opening to a full 90 degrees. This can be a problem and can create a funnel effect, slowing down the time of exit. Make sure that all classroom and hallway fire doors are able to open at least 90 degrees in order to create a good flow toward the exit doors. 
Room to line up
Having the classroom set up to line up without any hazards is a good practice. Make sure you leave a space from the door for the students to line up in a straight line. This will avoid students having to walk around desks especially when there is no power or the visibility is reduced because of smoke.
Exit bars open with minimum pressure
Test the safety bars on a regular basis (every day) on all the exits to make sure they are working properly. Having a door that is difficult to open in an emergency situation is not a situation you want your staff to experience. Every second counts and if one the doors can not be opened because of a faulty safety bar or handle, then make sure that an alternate plan is in place until the door is fixed.
Stairwells are clear of storage
The reason a stairwell usually has a lot of room at the bottom is to permit the people evacuating to assemble and await instructions if a particular situation occurs that the area outside is unsafe and a secondary exit needs to be reached. Having things stored in stairwells reduced the space that is available for people to assemble. Another point is if flammable objects are stored (cardboard, recycling bins, wood, etc.) these will elevate the risk of creating a fire hazard at the exit point.
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