I think you are making the right choice. Not only will you be away from home but grad school takes up quite a bit of time outside of school as well! I think it would be unfair if he was left alone all day, and then you weren't able to dedicate enough time for him later on (not saying that you will necessarily, but you will be tired when coming home and might not have the time to play with him or take him for walks. Plus you'll have lots of papers to write depending on your field!).
You can definitely visit him on weekends or whenever you have free time during the day. I know it's really tough, I am starting grad school too this fall and will have to be apart from my dog because I just don't see myself having the time to tend to her 24/7.
