Yes, the good Charter schools would have waiting lists.
As far as the public schools, you can research on this site:
MCAS - Boston.com. It lists all the schools in a particular city/town, what the school performance is like, and also what grades are included in the individual schools. You can easily tell if 6th grade is in middle school or not.
The exception to this would be a town where the elementary schools are located all on one campus, even though there may be seperate buildings housing different grades (like my town). So you may have K-1 in one building, 2-3 or 4 in another, and 5-6 in another, but they share the same property.