The "supposed to be...", is a really big problem.

First, it's factually wrong. Homosexuality occurs all through nature and it's not a mistake or random abberation. Presumably there's some advantage to having a percentage of any population not reproducing. Perhaps so that they aren't burdened with children and are free to fill other roles in their community, herd, flock or whatever. This increases the group survival/reproduction rate, even though they aren't reproducing themselves.

Secondly, "supposed to..." implies that there's something wrong with any non-heterosexual individual. It sounds like, at best, you'll accept their homosexuality as natural but, at the same time, you understand that they're actually defective. That attitude isn't going to lead to good things, and not something I would like to see widespread in society.

And finally, the fact that you would even say this points out the need for more education on this in schools, not less.