ISP Alumni meet monthly here in Prague (the 3rd Wednesday of every month from 18:00-20:00 (not held in December)) in a casual setting; the purpose is to simply connect ISP Alumni with old and new friends, in a relaxed atmosphere, who share the distinct honor of having attended the same school, and of living their lives as “Third Culture Kids”.
These monthly meetings currently take place at the Swan Club, which is downstairs at the Divadlo Kolowrat. ISP is a supporter of the Prague Shakespeare Company (which performs at the Kolowrat Theater).
If you're a Facebook user, check out this page to make sure that the meeting is taking place.
An annual Alumni Reunion "weekend" takes place each year in the spring (it's actually a Friday and a Saturday). Time is set aside for the official reunion years (those celebrating their fifth, tenth, etc year after graduation), and also for Alumni of all years.
To see this year's schedule, please visit this page.