Stay away from Willimantic! It is very dangerous (just moved out of there - very poor, lots of heroin and meth), and the school is terrible.
Windham High School is very bad (easy to score drugs on campus, arrests on campus weekly- I had friends with kids there and they moved to another town to get them out).
Brooklyn, Pomfret, Killingly are not bad/very nice (depending on where exactly).
I should warn you (I used to drive from Willimantic to Prov several times a month), that Rt 6 in the winter is pretty dangerous. Do not plan on driving at all if there is snow currently falling. Several areas are "reduced salt areas" to preserve natural wetlands. This means the roads are very slick.
It is a beautiful drive, I will definitely say that! But Windham county is not great if you have high school age kids.
Also, it was a 45 minute drive to a target from willimantic. Without traffic. It really is pretty remote compared to what I was used to.