Is the lesbian content optional, as In I get to choose whether it happens or not?
I wouldn't recommend playing this game if you are super averse to lesbian content.
It's a school filled with girls several of whom are bi or lesbian. As you would expect with no boys around they talk about and you see some of their exploits.
In addition many of the punishments include content that is more or less lesbian and in fact
I just can't imaging playing this game and getting anything but frustration out of it if you really hate lesbian content
If it's choice you are concerned about while there are some impactful choices, this game isn't designed for you to pick and choose love interests, mainly because they aren't really love interests in the standard porn game sense. Characters do have questlines but it doesn't really make any sense to avoid them, as again almost none of them revolve around romancing the characters
This all really stems from the way the MC is written, and it's one of the things that makes the game so good imo. He's very far from your standard porn game MC and in very interesting and engaging ways, but that also means the his interactions may not be satisfying to people looking for a dating sim type game. He does develop relationships with the characters and they are interesting and well done, it's just not a romantic thing for the most part.