My old 1st Sgt. is a teacher. he was at every training i was at so im assuming he didnt have any problems.
Crashbubba is right though, you should really look into your own jobs SOP's and regs. I was pretty lucky that my company itself (as well as my union) offered its own protection for active duty and reservists, but i think some jobs may be different. for example, if you get deployed because its your units rotation for deployment, you may be covered, but if you VOLUNTEER for deployment outside your unit, you MAY NOT be covered... its kinda jacked up, but i have seen stuff like that happen.