Studying takes longer to rack up. Playing the Quiz Game at the mall every so often gives more Academic points than studying. There's also a certain restraurant in Iwatodai that eating at increases your knowledge (can't recall what the name is). But yes, it takes longest to level up out of all the statistics.
Making a donation at the shrine also gives you Academic points IIRC more so if you're in "Great" status.
I think itís the duty of the comedian to find out where the line is drawn and cross it deliberately. - George Carlin
Play Quiz game in Mall, which gives +4 points and that is best possible way to rise Academic quickly - only if you have money to spend.. (still it is better than waste time at your room in night which only gives +2 points) Or you can donate 100 Yen in Jinja/Shrine for +5 points if you are at Great condition. Also study at your room in holiday gives +4 points if you are Good and above condition.
EL ELOHIM ELOHO ELOH M SEBAOTH ELION EIECH ADIER EIECH ADONAI JAN SADAI TETRAGRAMMATON SADAI AGIOS O THEOS ISCHIROS ATHANATOS AGLA AMEN - from SMT1 Opening