Is it obligatory to teach a left-handed child to use his right hand for eating, drinking, and writing, and does that have psychological repercussions on him?

The Sunnah is to use the right hand for everything honorable, such as eating and drinking. The majority of scholars dislike eating and drinking with the left hand, and some even deem it forbidden. Children should be accustomed to eating and drinking with their right hand, and gently encouraged to use their right hand for writing as much as possible.