Board Thread:Questions and Answers/@comment-112.201.49.165-20160509153409/@comment-33871937-20171207115301

The simplest answer would be plot convenience - Izuku needed to be placed near the bottom to give the audience a sense of how far behind he was. How Tooru got through the exams and ranked may be something even the author themselves don't know. I mean, he did actually forget to list two of the students rankings, and apologized for it.

If we get analyztical though, then yeah, Tooru would have to have gotten a bunch of rescue points or Kill Stealing. Perhaps both at the same time. Wait until the enemy is engaged with somebody else, and then 'save them' by attacking a weak point and securing the kill.