That’s a big call if you are relying only on hearsay.
Yes, there are international schools in Shanghai that don’t offer value for money. But there are at least two or three that would just about match the best schools on offer in the U.S. or Britain. As mentioned above, these are ones that people move their kids to after unsatisfactory experiences with various institutions.
Yes, there are some spoiled brats. But as a general rule I am far happier for my daughter to be friends with the kids at local international schools here than many I have encountered back home. As a generalisation they are higher academic achievers, with stable family backgrounds, and a more mature worldly outlook.
My two yuan worth anyway…