Study / English or German speaking school in Poznan [2]

Hello everyone, I need your advice and experience regarding schools in Poznan. My children, 14 years old and 9 years old, are German-speaking and speak English because they go to an English school. We will probably move to Poznan for 2 years.
Could you please tell me about your experiences with the English and German-speaking schools in Poznan?

(International School of Poznan, The British School.... are there any other alternatives?( What are these schools like anyway?
Thank you very much!