I don't like it when after-schooling programs mislead parents. I got an email from one my children attend with the first sentence saying

"As you might know , AMC 8 and AMC 10 tests are the most prestigious tests to the results of which majority of colleges pay attention."

There are two things wrong with this (ignoring grammar).
(1) The majority of U.S. colleges are unselective, so they certainly do not expect high AMC 10 scores.
(2) The minority of very selective schools care about what the student did in high school. So the AMC 10 score could matter, especially at a place like MIT or CalTech, but the AMC 8 score matters only to the extent that it predicts the student's scores on higher level AMC tests.