I like firstlast@school.edu. Email addresses with middle initials can be hard to remember. Having the first name in the email also reminds the receiver of your first name if you forget to include in an email. My second choice would be flast@school.edu. I would prefer that second choice if your name is difficult to include for some reason, for instance a hyphenated name. (e.g., should the name be anne_mariejones@college.edu or annemariejones@college.edu?)
No offense, but you’re overthinking this. I highly doubt employers are judging you if your full name shows up or not.
If it really matters though, firstlast@school.edu or fmlast@school.edu are more aesthetically pleasing to me.
But be aware that those with common names may find that the desired email address is already taken. Also, if two people have similar email addresses, the likelihood of email being sent to the wrong person increases.
But also be aware that if the student’s name is common, there may already be someone with the desired name-based email address. If two people have similar email addresses (e.g. FirstLast and FirstLast2), expect lots of mail to end up going to the wrong person (without the sender knowing, since the wrong email address will not bounce).
When we were doing this for a local school (not college) we went with initials to reduce the information available to the creeps contacting the kids. There’s a lot of difference between stjohnson and Sarah.
EDIT: None of this matters as long as it isn’t an eight digit number or phish69. A good email name format is functional and boring and has an easy way to separate duplicates. Your Snapchat account (or whatever) can be goofy as long as you maintain one face that’s for business.