We more or less HAVE to send invitations home via the backpacks. The directories usually do not come out until November, and even then, less than half of DD's class was in it. (Her birthday is before the directories come out.) There is no address listed in the directory, just a phone number. You can't mail an invitation to a phone number. We live in a very mobile town, and families constantly move. Even if they were listed in the phone book....and a large percentage are not.....by the time you get the phone book, they have moved to a new house. Or they are too new to the area to even be in the phone book. Many don't have a land line at all anyway.
There is no class email list. There is no class roster. The privacy issue is bordering on paranoid.

Last year, DD's teacher wouldn't even confirm how many girls were in the class, let alone if I had the names correct. So I rely on DD to get the names of every girl, she writes the names on the envelopes and in the backpacks they go.
DD's school has a policy of switching the kids around every year and making certain a child is placed with NO MORE THAN two children from the year before. In other words, when your kid walks into 2nd grade, at best, they will only know two kids from their first grade class. I hate the policy, but there it is. My feeling is that it hinders making long term friendships, but they seem to think it makes the kids flexible and able to adapt. I think it teaches them that you can't count on anyone to be there from one year to the next, so why get invested? But that is another thread.........