May I suggest that you schedule a tour of both Darien & New Canaan High School.
The differences will become clear.
I see you are moving from Irvington NY population approx. 7000.
I lived in the Irvington area for 7 years before moving to the New Canaan (population 24,000) /Darien (population 20,000) area. You will love this area.
Please call me if you need help making a choice between these two great towns.
When buying a home in this area, the pluses and minuses are anecdotal and personal in nature. If youve narrowed your seach to these two towns you can rightly move on tothe issues of location,amenities,beaches etc and let the school issue rest..
If you wish to get an insider view of Darien,visit my blog, http://www.thegoldcoaststandard.com
Here is a link to the State of CT Dept of Education website where you can look up the differences in the school and school districts that are pertinent to you... http://www.csde.state.ct.us/public/cedar/districts/index.htm
Should you require additional information don't hesitate to contact me. Good luck!