AITAH for catching my sister's boyfriend in a lie about what school he graduated from?

My sister brought her new boyfriend over for the holidays, it seem serious but now she is upset with me cause apparently I ruined her relationship.

Overall he seemed cool, and I hope I did not ruin anything for her. What happened was during dinner my dad asked what he did, he told us he was an attorney which is cool. everything seemed to go well, like I said overall he was a cool guy. Subject of family came up and he started to talk about his family, they also sound nice. My dad did ask what brought him out here. He said he went to law school here, and I asked where he said SLS, I said oh shit so did I. I started to talk about school and stuff but he become very uncomfortable.

The vibe kind of died at that point and the rest of evening was extremely unpleasant. They cut their visit short and it appears it was all my fault according to my sister. I admit I was a tad overzealous because I have been out of the game for awhile now. I took a break to help our parents care for our grandparents. It is not a bad deal, so I do not mind but I did get excited to talk to someone I potentially may have known in passing.

I am torn I tried to apologize but my sister is not having it. I did not think what I did was wrong but even so I did apologize. My mom is also kind of miffed since she does not see my sister often and they cut their visit short.

Should I have not said anything cause as my mom said he clearly became uncomfortable when I said I went to the same school.