Here’s a bit of medical advice from the July 15 1952 edition of the Toronto Daily Star.
The conclusion of this article includes this:
Few mistakes will be made if parents follow the law of averages and teach all youngsters to use the right hand. Those who rebel are the “lefties” and should not be forced to change.
Wikipedia has an article about bias against left-handed people that is interesting reading. In 1932, only two percent of Americans wrote with their left hand, with the number rising to 7 1/2 percent in 1946, 9 percent in 1968, and 12 percent in 1972. However, many other countries encouraged or forced the use of the right hand, including the former Soviet Union, in which all children wrote right-handed.