At the point when Lucas and Hailey realize their are right next to each other and right next to Nathan's as well, Lucas has short hair that is not really styled in any particular fashion, no facial hair, and a dark blue shirt on. In the next scene, where he is walking with Brooke to her locker, his hair is about a quarter to half inch longer and styled, he has noticeable facial hair, and a shirt that is a tad bit lighter.
Haley says she has locker 141 and Lucas has 143 which would make Nathan 142, but when Nathan is closing his locker, it's locker 139.
Haley says she has locker 141 and Lucas says he has 143 and that they must be alphabetical. They look up and see Nathan. However, if the lockers are alphabetical and they all have the last name Scott, it would then be alphabetical by their first names. Haley and Lucas would have consecutive numbers, not one between them, as N comes after both H and L.
When Haley and Lucas are reading their predictions from previous years, Haley reads one that says 'this year I will volunteer at the tutor center.' Previously, she had told Nathan that the reason she started at the tutor center because she had cheated on a test. If it was something she planned because she cheated the previous year, Haley wouldn't need a prediction. If it was something she did in the middle of the school year because of a test she cheated on, it wouldn't be in her predictions.