As long as it’s innocent and both respect boundaries, I don’t see a problem.
Not a college student until this fall so I can’t speak on personal experience, but I will say that I went to a very small high school (we’re talking >125 students for the entire school, not just my class), and hanging out with teachers was completely normal, though it was in a setting more approved for 13-18 year old’s rather than bars and karaoke. There was a math teacher that invited students to her house where she and her husband put on little guitar concerts and had barbecues biweekly in the fall and spring. There was one teacher that retired but still regularly posted sign-up’s at the school to take a few students fishing, and it was always a lot of fun. There were several younger teachers and staff members who took groups of students bowling and to the movies and theme parks, though it was more motivated by the fact that many of the students were from low income families who didn’t get to do things. We took school sponsored trips every year with our graduating class to go camping for a few days, and the setting was always more social than professional; you were brushing your teeth right next to your teachers, everyone was in their pajamas, and every tent had one same gender teacher sleeping in it to make sure no one was sneaking off. We were an inter-district school, and teachers and students often carpooled, since a lot of students were coming from an hour away and the trip was hard to make twice a day, so teachers who lived nearby picked them up.
I’m well aware that normal high schools don’t operate this way, but it without a doubt improved the quality of the education I got there. If I was having trouble with a class, it helped that I could access the teachers so easily; on the syllabus, every teacher had their cell phone number if you needed help with homework or were going to miss a class. There was definitely potential for disaster with such a close student-teacher relationship, but they were selective with their hiring and staff felt like second parents.
I think it’s always risky for students and teachers to interact outside of school, but it can also be extremely beneficial, provided there’s no bad apples to spoil the bunch. A lot of teachers genuinely care about their students and want to see them do well, so inviting them to have dinner with their families or a group of students out to help the kids relax and not be constantly stressed out can be extremely beneficial.
Back in the stone ages, my 3rd grade teacher invited a small group of us to her home over the summer to play bridge and swim in her pool. Her husband grilled lunch for us. It was lovely and I still remember that day fondly.
We saw many teachers at graduation parties and senior events at DD’s HS (eagle scout ceremonies, recitals, show type stuff). My daughter and her friends routinely had lunch with the calc teacher and once they graduated, were “allowed” to follow teachers on social media. I know my daughter has FaceTimed with some HS teachers from college just to say “hi”.
So far in college, she eats dinner with one of her professors every week (in the dining halls), and has gone with other students on a hike with the same professor.
The honors profs and staff that have offices in her dorm have an open door policy and students seem to really love to hang out with them.
I love that they have non academic interactions. It makes it easier for students to approach professors for help, to reach out to volunteer in their labs, and just fosters collaboration on a whole.