Hi prisma,
You can't compare their standard of Mandarin with local schools and maybe Suzhe. But for a bilingual school, I would say it's pretty good.
You will be surprised to see many non-Mandarin speakers doing work with the Chinese teacher. Besides doing individual work in Chinese, there is a daily circle time with the Chinese teacher. She will either read a book, sing songs, etc. My daughter speaks mainly English at home but she loves to do the Chinese work and adores the Chinese teacher.
In terms of writing, it depends on the child. Some children are not interested in writing and the teacher will not force them to write. My daughter has always loved writing and she is writing daily. She is 4 years old now.
V