I would strongly suggest instead of using A-L and M-Z to use bus routing as the way to determine what days students attend. The reason, if your system is like ours, we have so many blended families with different last names. It makes better sense and its a better use of resources for transportation. Just a thought that you may want to pass on to the decision makers up the food chain.
Our superintendent has released a statement on blended families and is allowing those kids to all be sent together. I'm just a lowly peon with one foot out the door. I doubt they would take my word on anything like this. They all seem to think they are all smarter than teachers anyway, so let them find out on their own.