Life is much more complicated than the middle school definition. Some of the more interesting species are “sterile” crosses that have overcome the sterility. For example the ancestry of wheat.

Wheat is mostly a hexaploid aka 6 copies of each chromosome. It arose from a triploid interspecific cross (triploids are always sterile) that spontaneously doubled (hexaploids are fertile).

As a hexaploid it can be crossed to diploid rye to produce fertile offspring called triticale (tetraploid). Crossing triticale to either wheat or rye creates sterile offspring (pentaploid & triploid)

So are they all one species because they can sometimes produce fertile offspring?