Tallulah,
Since you want to keep going, let's dig into Lexington, for the following reasons:
1. I don't live there.
2. Lexington High School is widely considered a gold standard among public schools.
3. It is mid-pack in terms of housing costs among the top school districts.
But first, let's back up. It is theoretically possible for a homeless family to have their child study in Phillips Academy for free, but that's certainly atypical. Everyone else will pay for housing. So in that vein, let's compare Lexington to a neighbor equally close to Boston, Waltham, where the schools are so-so and try to discover the "good schools premium". Note that I am ascribing 100% of the cost difference to schools, and completely ignoring that Lexington is a desirable place to live because of its rich history.
Suppose a family is renting because they haven't saved up a downpayment. They could rent a 2800 sq ft , 2.5 bath place in Lexington for $3000/mo.
http://www.zillow.com/homes/for_rent/Lexington-MA/house,condo,apartment_duplex,townhouse_type/56496978_zpid/19005_rid/days_sort/42.512475,-71.139822,42.389487,-71.309423_rect/12_zm/?view=map
In Waltham, the best deal I could find was a place with 3200+ sq ft, but it only had 1.5 baths. It was available for $2100/month. I will go out on a limb and say it's possible with enough searching and patience you could do better in Waltham at say $1800 per month.
So in this case the "good schools premium" is at most 12* $1200 = $14,400 per year. And for that you could send any number of children to the public schools there, for free.
Let's move onto buying a home with a 20% downpayment and a $600K mortgage, or a $750K target. Buying a home in these towns is a multi-month process, but if you had to buy something "today", there is one close at $780K with 3 bedrooms, 3 baths and 2226 square feet:
http://www.zillow.com/homes/for_sale/Lexington-MA/56491151_zpid/19005_rid/0-800000_price/0-2947_mp/days_sort/42.512475,-71.139822,42.389487,-71.309423_rect/12_zm/0_mmm/?view=map
I will leave it as an exercise for you to determine the "good schools premium" vs. buying an equivalent property in Waltham, and the difference in mortgage payment. And as I said, Lexington is mid-pack. Further away from Boston, homes are generally cheaper in many towns with great school systems.
