Should I pick a teacher who gave me high grades?

It’s worth considering, but it shouldn’t be the only factor. A teacher who gave you high grades might not necessarily know you well enough to write a detailed and personal recommendation. There’s also the chance your teacher gave everyone in your class high grades; if so, your teacher may not actually have anything notable to talk about you. Instead, pick a teacher who knows you best and shares your interests and passions. A thoughtful, well-rounded recommendation is more impactful than one solely based on high grades. Just as how you would like to be showcased holistically, choose a teacher by assessing their whole character as well.