My attempt is:

memento quos te praeisse (speaking to an individual)
mementote quos vos praeisse (speaking to many people)

this has more of a sense of those who have led the way rather than just walked ahead

or possibly

memento quos ante te ambulavisse
mementote quos ante vos ambulavisse

this is more along the lines of those who have walked ahead

If you or a relative called Southend High School today, I answered your call and have passed the message on, this is my personal attempt (I studied Latin at university - but did not do much English into Latin!) - I cannot speak for the school.