It appears to me that the only male child who Vito wanted to keep "out" of the business was Michael. He sent him off to college to try and provide a "legitimate" life for him. Other than Tom, it doesn't appear that Sonny nor Fredo had a formal education. Nor does it appear that Vito had any type of formal education at all. When Tom broke the news to a recovering (gunshot victim) Vito that it was Mike who had gunned down the Police Captain, Vito appeared to be very sad and resigned to the fact he had failed to protect Michael from the "business."