would very much like to send my children to Polish school and to learn Polish language and culture, but the fact remains that one of my daughter is already in 8th grade of an English Convent and it will not be easy for her to study all the subjects (Math, English, Geography, Arts, Chemistry, Physics etc) in Polish .
Poland is different to England in that they speak Polish, as Lukasz said, there are 'some' schools that teach lessons in English.
PLus she has to take her O' level (Cambridge )exam in next two years. I
You will have to see if Poland actually participate in the Cambridge O' Level, this is an international qualification and not to be mistaken with an English O' Level qualification.
I just had a thought that there must be some people like as migrating from Canada, US or UK to Poland under similar circumstances
They either send their children to schools that teach in Polish or pay for private education, families from the UK are usually in a Polish / English relationship and the move is one for life so therefore the children just go to normal state schools.
Usually in many countries there are English schools for children of foriegn officials living different countries for missions or so.
Again, foreign officials would send their child to a private school that teaches lessons in English, Poland is not for life and not their home.