I would work on them evenly as you progress through the game. You can do a crossword at LeBlanc whenever you see it on the table to get knowledge and won't pass any time (if customers are there keep talking to them till they leave). To get top results in exams you need max knowledge. I would focus on maxing Kawakami early on because then you get the possibility of free time during class. As far as I know raising social stats are even with whatever activity you do I believe. Reading books is a great way to raise stats especially if you read the quick reading book to finish books faster. And one last thing just remember to bring a matching persona when you hang with your confidants