From traditional school to international school

Hi,

My sister studys in a traditional school now. She has applied Harrow Int'l school and she got the offer. However, english is her second language and she speaks cantonese for most of the time. i am afraid that she wont be able to get along with the other student. another problems that raise my awareness is about the curriculum. She will be in form one in 2012 but Harrow offers her the place in year 8, which is equal to form 2. Though i learn that the course in int'l school is not as demanding as in traditional school. Should I let her to study year 8 instead of year 7. my concern is about the language. Are there any parents here can share their experience when their children change the school from traditional school to international school and any issue that i should be aware of?

Thanks very much.