Matthew,
I came across your post when trying to find information about my grandmother. She attended Bridgman in Beijing. I thought it was a high school but the age wasn't lining up for me. Your post was the first I heard of there also being a middle school. Do you have any further information on the school? I do not know when she started at Bridgman but she had one more year left, around age 14, in 1937.
Thanks,
Lara