I agree he shouldn't be in a classroom again; it's definitely a severe case of overstepping the mark...
*But*, he did not "abduct" her, regardless of what statutory law says.
Also, he's treated her well, is clearly actually genuinely in love with her, and I'm sure he did not do any of this lightly, knowing the possible repercussions.
If she was my daughter, an initial shock followed by deep anger would by now have given way to more reasoned feelings. Knowing that my daughter was being treated well by him, that she trusted him and loved him, and her feelings were reciprocated would be enough for me.
Better than a male classmate who was just looking for his first shag to impress his mates.