When selecting who to send a SOE to, keep in mind that they are primarily used to measure your leadership potential. That may have some bearing on which grade level teacher you send it to - ie how much of a leader were you in your freshman/sophomore year compared to as a junior/senior.
You may have fond memories of your sophomore algebra teacher but does that really help your case in gaining admission, especially considering that algebra is below the admissions criteria for qualification (pre-cal or trig minimum). If there is an issue with any math aspect of your file (test scores, grades, qualification standards), the first place they are going to look is that Math teacher's SOE for insight into your capabilities.
There is no "right" answer on who to have write your SOEs, but as in life, there are better answers given each unique situation.
SOE is relatively a straight forward matter, so no reason to overthink it and spent extra effort. I have never heard of a candidate getting an appointment because he or she got an great SOE. For West Point, it's worth about 10% of the evaluation, so one SOE might be worth 3.3%. My RC told me that a bad SOE can hurt a candidate, but that can be mitigated with a good interview or good LOR.