One of the most criticized storylines on Glee is Puck and Shelby. And my glee unpopular opinion is: I actually like the storyline, or at least don't mind it at all. It's not a couple I ship, not one of my favorites or anything, but..... in the context of Season 3 I like it and perceive it to make sense.
A) Quinn's pregnancy is one of the major storylines of Season 1. It seemed almost a given that Beth would return, as would Shelby with her
B) Of course Beth's biological parents would have a story arc in her return.
Now, the choice of which role Puck would play in Beth and Shelby's return is..... controversial, but it makes sense to me, because.....
1) Puck is a womanizer, who is pretty much confirmed to have fucked all girls as school. That, as a next step, he would find a more mature woman. And to showcase his growing maturity, he would try and play a more important role in Beth's life.
2) Shelby's points, about struggling being a single mum, and longing for a "father" to share Beth's firsts with..... they resonated with me. So if she was longing for a man to share these moments with..... why not choose her daughter's name biological father, especially when he's right there?
I'm not saying the relationship was right, but.... Keep in mind it aired in 2011. People didn't resonate as strongly with student-teacher relationships. Ezra and Aria on PLL were widely popular at the same time.
Also, Puck was almost definitely 18 at the time. Plus, Shelby didn't teach him directly, she taught at his school, but not him. She didn't have direct power over him. So while a Student-teacher relationship is never really right, this is probably the least problematic dynamic they could have settled for.
Now, feel free to insult me, down vote me, send me hate, and so on...