St. George's is the English / International school. http://www.stgeorgesschoolcologne.de/
For something completely different there's the Freie Demokratische Schule in Nippes. http://www.freie-schule-koeln.de/
I personally don't like the public system as it funnels kids into three different schools at around age 9 or 10, and which one they end up at will likely influence their future career options. I just think 10 years old is too young to be directing a person towards their career.
We're going to try Waldorf, but our son is just one and will be starting their Kindergarten in a year, so I have no experience. I have learned a lot about what a Waldorf education is through reading the Waldorf forum here as well as a few books.
Hey are you into meeting up with other AP / NFL mamas in Cologne? There are a few of us regularly meeting, we'd love to have more.
Mama since 2010
Multicultural living in Europe
Sorry it took so long for me to respond, but I was waiting for a response from a friend to your inquiry. His daughter goes to the Gemeinschaftsgrundschule Stenzelbergstrasse in Klettenberg and they are happy enough with the school.
Me 41, single mom to dd 4/2001 and ds 7/17/2010
International Peace School in Widdersdorf.
My kid isn't old enough yet to go to school, but I read one of their flyers and liked the concept.
They're quite expensive though, I believe.