Okay, you may not like what you'll hear, but it really depends. There simply are too many variables.
Lots of law students intern at SAM. These days, internships aren't even that selective - which is actually quite unfortunate because it effectively dilutes the quality of the intern pool and makes it harder to get recruited based just on internship performance. It's worth noting that only an extremely small minority will get called back and fewer still get placed. Let that sink in first.
To be considered for a call back, you need to have received very strong positive feedback AND the associate you worked with must have recommended you for a call back while filling out your appraisal form. Similarly, for a PPO, the associate (and the partner to whom he reports) must recommend you. Unless this happens, you can pretty much forget about call back.
Generally, a PPO isn't given to someone who hasn't interned with the firm at least twice, though, I'm sure exceptions exist. Factors that matter are, your law school, grades, performance, attitude while interning etc. Again, not every team looks to hire right out of college (which basically is what a PPO is), so it's best to check with the person who you worked most for what the scene is. Again, how important each of these factors is depends on practice area. Some practice areas/teams aren't as selective, others are.
Reaching out to HR won't help. Without your appraisal being processed, they'll not be able to really do anything.
As others have already said, it all depends entirely on your team. I'm basing this answer on my personal knowledge, I've interned with SAM last winter.
The practice now seems to be to assign a Training Guide (fancy term for essentially a mentor) to each intern. Your TG will typically be an SA or a PA, basically the seniormost person in the team below a Salaried Partner.
The TG has to fill a feedback form at the end of your tenure. Three things can happen thus: (1) you get recommended for a PPO interview, (2) you get recommended for a callback, or (3) nothing. Practically, I suspect the TG will consult the Partner on the team before they make any recommendation. So, the key is: do great work for, ask for feedback from, and ensure you're noticeable to, both the Partner and the TG.
There's no hard and fast rule that you won't get a PPO without a callback. I know because I got recommended for a PPO interview after a single 6 week stint. However, to be fair, a PPO after a single stint generally appears to be rare.
Please try to get your internship extended, to an aggregate of at least 6-8 weeks. A recommendation from the Partner, or TG, will practically guarantee it.
Lots of law students intern at SAM. These days, internships aren't even that selective - which is actually quite unfortunate because it effectively dilutes the quality of the intern pool and makes it harder to get recruited based just on internship performance. It's worth noting that only an extremely small minority will get called back and fewer still get placed. Let that sink in first.
To be considered for a call back, you need to have received very strong positive feedback AND the associate you worked with must have recommended you for a call back while filling out your appraisal form. Similarly, for a PPO, the associate (and the partner to whom he reports) must recommend you. Unless this happens, you can pretty much forget about call back.
Generally, a PPO isn't given to someone who hasn't interned with the firm at least twice, though, I'm sure exceptions exist. Factors that matter are, your law school, grades, performance, attitude while interning etc. Again, not every team looks to hire right out of college (which basically is what a PPO is), so it's best to check with the person who you worked most for what the scene is. Again, how important each of these factors is depends on practice area. Some practice areas/teams aren't as selective, others are.
Reaching out to HR won't help. Without your appraisal being processed, they'll not be able to really do anything.
Hope this helps
The practice now seems to be to assign a Training Guide (fancy term for essentially a mentor) to each intern. Your TG will typically be an SA or a PA, basically the seniormost person in the team below a Salaried Partner.
The TG has to fill a feedback form at the end of your tenure. Three things can happen thus: (1) you get recommended for a PPO interview, (2) you get recommended for a callback, or (3) nothing. Practically, I suspect the TG will consult the Partner on the team before they make any recommendation. So, the key is: do great work for, ask for feedback from, and ensure you're noticeable to, both the Partner and the TG.
There's no hard and fast rule that you won't get a PPO without a callback. I know because I got recommended for a PPO interview after a single 6 week stint. However, to be fair, a PPO after a single stint generally appears to be rare.
Please try to get your internship extended, to an aggregate of at least 6-8 weeks. A recommendation from the Partner, or TG, will practically guarantee it.