Alyssa, one test score at one point in time is only that - one data point. It might be representative of either ability or knowledge, or it might be low due to any number of reasons (do you remember if you were feeling well that day? Did you run out of time on the test? Etc). Also - are the 70s and 80s actual scores or percentiles? The ERB reports I've seen usually just show the scaled scores and percentiles.. and I'm just guessing that if you recieved a score in the 70s that would have to be a raw score? Did you get either percentile or stanine scores? (please don't feel like you have to answer that or share #s, just wanted to make sure you didn't accidentally mistake one type of score for another).
I wouldn't rethink any career paths or college plans yet - no way! I'm curious why you are taking the ERBs - is that the brand of standardized score your school uses for yearly assessments? Since you're a junior in high school, are you planning to take the PSAT (or did you take it already?). Have you considered taking either the SAT or ACT this year?
I suspect that your scores on the SAT and/or ACT will be what the colleges you apply to will want to see, not your ERBs. JMO, but once you're in college - what it takes to be successful never fully hinges on any one test score or even necessarily on having extra-high ability - it takes motivation, hard work and drive. Passion doesn't hurt either

Good luck!
polarbear