Good luck with this one - Melrose school system is already beyond over-load! Special consideration should be given to people like you! I bet most of your property resides in Saugus but then the fact that you are required to vote in Melrose doesn't make sense. Given the choice between Saugus and Melrose- I would fight this - although Saugus just built a state of the art high school!

Tell them that your bedroom and your sons bedroom is in the Melrose part of the property. He sleeps in Melrose.
This may help.

I almost believed you until you said that Melrose has a great education system.

Can you find the previous owner to get the low down. who told you he cant go to Melrose? Does your address say Saugus or Melrose I think if you provide the required documentation when registering they cant deny you.