Classrooms are getting much more diverse in every Massachusetts county except Suffolk (Boston), and the Bay State is an outlier in several immigration trends — particularly in our paucity of Mexican-born residents. Those are some of the more interesting points gleaned from the interactive map and charts that accompany a discussion about immigration in today’s New York Times.

The map allows you to see immigration flows from specific counties over the past century. Not surprisingly, Boston has been a focal point for Irish immigrants for more than 100 years, even as the number of transplants from the Emerald Isle has steadily fallen. On the other hand, few Mexican immigrants have made it to the Hub even compared to other Northern cities such as Milwaukee and Seattle. Unfortunately, the map does not allow to track trends for several immigrant groups that have high concentrations in Massachusetts, such as Brazilians and Haitians.

The Times package also includes charts on the “diversity index” of school systems in every US county. (The term is defined as “the percent chance that two students selected at random would be members of a different ethnic group.”) As of 2006, the diversity index at the national level was at 61. In Massachusetts, it was at 44, up from 28 in 1987. During that period, the diversity index went up in every Bay State county except Suffolk, where it stayed frozen at 69 (even as the percentage of non-Hispanic white students continued to fall, from 32 to 18). Springfield’s Hampden County had the second highest score on the diversity index (57, up from 45).

The biggest jumps in the diversity index were outside of Boston and Springfield: Nantucket (from 8 to 36), Essex (from 25 to 45), Middlesex (from 22 to 40), Norfolk (from 13 to 31), and Worcester (from 18 to 36).

The lowest diversity index numbers were in the west (Franklin County, at 14, and Berkshire, at 19) and on Cape Cod (Barnstable, at 17). The South Shore’s Plymouth County went up from 15 to 28, but with an 84 percent non-Hispanic white student body, it is the least diverse county in the Boston metro area.