input on St Martins, Florida Day or Belgrano Dayschool?

We are moving with our 2 sons this summer and will put them into school for 20 months. My husband is a Porteno and swears that we must live in Belgrano or nearbye. 

We have identified 3 schools -
St Martins
Florida Day school
Belgrano Day

Does anyone have any input on any of these? My older son will have just finished kindergarden at a lovely progressive school where they let the boys run - i look at the school websites with all the kids sitting quietly in uniform and wonder if he'll manage ok!

Thank you!