How To Increase Your Students' Happiness In Fire Emblem: Three Houses
A motivated student is a happy student, and a happy student learns better. If you want to max out your students' abilities and make sure they meet advanced class requirements, you'll need to train them during the weekly lecture. That requires Motivation. The more Motivation that your students have, the more lessons that they can handle during the week, and the faster their stats will rise.
Thankfully, increasing motivation is pretty straightforward. Would something make a person happy in real life? Then it'll make characters happy in Fire Emblem: Three Houses, too. Inviting a student to join you for a social outing, like eating, cooking, or singing in the choir together, will motivate them. So will giving them gifts. Taking a rest day instead of exploring the Monastery will prevent you from engaging in social activities, but it'll also raise your House's Motivation. If all of your students are down in the dumps, it might be a worthwhile trade-off.
When you're training your character and he or she does particularly well, you'll get the opportunity to praise them. If they do poorly, you can either console or scold them. Praising a student always gives them a little more motivation, but the results of consoling or criticizing depends on their personality. During the first lecture of the month, characters will also ask for advice. If they like your answers, they'll get some Motivation points.
Finally, good performance during a battle can motivate a character, too. If there's someone that you really want to train, make sure that they get the most kills during a fight. That'll make them the battle's MVP, which maxes out their Motivation all in one go.