When I was studying for Orgo and the MCAT I would announce to the kids that I was studying from, say, 1:00-1:45. Any snacks, drinks, etc needed to be asked for right now, before I started. Then I would set them up with said snack and a favorite TV show. (I often planned around their shows!) The more often I did this the more used to it they got to be. after a while I would hear them telling each other not to bother me until the show was over. ( the TV show gave them a concrete start and ending point.) It did help decrease the disruptions.
Still, I studied when they were at school or at night as much as possible. I would even wake up at 5:30 to get an hour in before the day started.