TexasCHLforum.com

First off, let's assume the building is owned by the church and not a 'school' entity and not posted with a 30.06 sign.

Now, while there is not really a solid definition on this, here is the majority train of thought: If the school uses shared space (i.e. school during week and church use on Sunday or other times), then it is only off limits when there are students there. If the area is exclusive use of the school, then it would be off limits at all times.

Pretty simple way to break it down, and if you would be challenged about carrying in the area of the building it would give you a argument for defense.