The art is good, the characters are good (my favorite is Audrey), but the game's structure needs work.
It's been touched on, but quests are mostly you bouncing back and forth between npcs, and fetching resources. In my opinion, they could be cut down more to reduce repetitiveness, or at least condensed into longer single dialogues to save time for the player. Material fetch quests could maybe be less common but more important.
Additionally, for an adult visual novel, adult scenes are few and far between. The game would probably benefit from a pass that intersperses more adult scenes with the main characters (the teachers) throughout the main story, instead of just relegating them to individual romance story lines. Right now, if you like a main character, then you just have to hope her individual story gets updated. There should be more to see of everyone in the main story.