People expect to much from me?

im a junior at school and we just had back to school night and for some odd reason my mom wanted to come so i was like sure whatever floats your boat. then 3 of my 6 teachers (which i have b in) said i don't try as hard as i can and they "felt i could do better"..... at first it didn't bother me until my last teacher said he could be a all A student if he puts his mind to it. At that point my mom started to believe my teachers and wants me to get all A's which i never had. So here's my Q why do i have to try harder than i normally would because some teachers decided to set the expectations to high? Should I if so Why? and how do I get people to see me rather than some all A student(not the first time iv'e been mistaken for a all A student)?