I tell my wife that play is also important for a child's well-being, but she won't listen. How much studying is too much?
Your letter clearly highlights a major chasm between you and your wife in terms of your parenting philosophies. If this situation is left unchecked, I predict that your kids will begin to exhibit more and more behavioral and emotional problems as they age, resisting your wife's demands. Your marriage may suffer as a result of maintaining this academic schedule for them. You and your wife must seek professional family counseling in order to see how these unrealistic academic expectations are harming your kids. You have been going along with her demands, albeit with heartfelt objections and concerns. Please get some professional help for yourselves as parents before you have to get professional help for your kids' serious mental health problems. Just because they currently are "with the program" and perhaps succeeding academically does not mean that they are not being harmed in many ways. Your wife needs to discover what is driving her unrealistic demands regarding your kids' academic performance.