The Church doesn't make any statements on the age of the earth, so that's a personal belief that is up to you to decide. The Vatican scientists tend to believe in theistic evolution with an old earth, as do most scientists, so that's what I go with.

But this science teacher of yours appears to be making a sarcastic remark when he referred to "biblical scholars." That is a sign of an atheist pretending to know what biblical scientists believe. So while he probably knows what he's talking about when it comes to science, he probably has no idea what religious people actually believe and what religion is. Just because someone knows a lot about one subject, doesn't mean they know anything about another subject.

Do not allow him to put his nonsensical atheistic beliefs into your head. Many Christians, and especially Catholics, understand that science and religion go together amazingly well and to truly understand one, is to understand the other. Some of our greatest scientists were and are Catholics.