Double Past Tense?

Double Past Tense?

Can you please tell me which one of these sentences is correct, and why?
Thanks!
Lastly, my experience as a teaching assistant helped me throughout the
course as I shared what I did to make my students succeed in the courses
that I helped teach.
versus
Lastly, my experience as a teaching assistant helped me throughout the
course as I shared what I did to make my students succeed in the courses
that I helped taught.