How do you manage someone who is junior to you (in seniority) but older than you (took time off and some class year cuts) and they keep trying to bring up how they’re older and should be more senior but for the class year cut. They are not doing a good job substantively so I’m trying to train and manage them but having issues - constantly getting pushback, minimizing my comments as subjective etc and not their mistakes. I’m a first year female partner and the associate is a male if that matters

Oh, it matters. You need to be very direct about performance, without the overlay of the age thing, but including the reluctance to accept feedback.

I am a few years older than my boss but i respect the hierarchy and get on with it. Don’t let his age prevent you from doing what you have to. You will need to exert your authority - you are partner for a reason! Well done by the way, great achievement.

I’d note these issues in their review and not work with them again. I manage a lot of people older than me and I haven’t had this issue - this says a lot about them rather than about you

I would emphasize that the firm has a standard when it comes to work. He is not meeting it and if he continues to show that he is unwilling to implement feedback and improve, you will have to remove him from your matters. I'd keep a written record/redlines of all the feedback you've given him and his responses/email responses as well just to CYA

It’s always an odd dynamic when you’re the boss of an older person. I often feel like that with paralegals and assistants, but I just remember that I worked hard (and was lucky enough) to be in the position I’m in. But as a partner, you’re the boss. It doesn’t matter how old he is. Sounds like he’s not taking critical criticism very well. You know how to handle that? Bring it up during his review. He will probably resist it again when he gets the reviews, but let him dig his own hole. However, be genuine in your reviews. I used to work with a female partner who was literally lying on the reviews and would tell me I don’t take critical criticism well just because I had asked her to provide examples of when I did XYZ that she accused me of.

It matters. You need to have a conversation with them and be direct. Not a partner but as I get more senior I realize a lot of people are never told they’re f*cking up. They’re genuinely clueless and think their behavior is acceptable.

This person literally works for you. Spell things out once and observe whether there is progress or not. Explain that it’s not just the work product that’s lacking. Explain how their attitude isn’t meeting expectations.

If they get it, great.
If not, you stop working with them and escalate your comments in a review.

How are they junior to you if you’re a first year?

You are a partner. You were elevated to partner for a reason. If they were that good, they’d have come over as a partner or been elected regardless of class year. So tell them they need to shape up and internalize your feedback or they won’t have the skills necessary moving forward.