According to The Theological Dictionary of the New Testament the Greek word αἱρέσεις denotes a “doctrine” and especially a “school.” It did not have the negative connotation until shortly after Christ. The same can be said for its Hebrew equivalent:
The corresponding term in Rabbinic Judaism is מִין, which can mean both αἵρεσις and αἱρετικός. Like αἵρεσις in Josephus, מִין denoted in the first instance the trends and parties within Judaism. But soon, when certain minim separated themselves from the orthodox Rabbinic tradition, it came to be used only of trends within Judaism opposed by the Rabbis, and therefore sensu malo. The term thus stigmatised certain groups as “heretical.” (Gerhard Kittel
Therefore when we look at the verse, it is like saying there must be divisions among you into different schools of thought (not necessarily negative) so that those who are approved, or the true church, might stand out from among the rest. I think the idea is therefore that God has intended that the church be tested with all sorts of criticisms and deviations of teaching, forming into various splits, so that his church would be refined like gold in a furnace. For example, if there were not constant attacks on the divinity of Christ in the early church history and like wise attacks on his true humanity, then the church would have not separated herself from the world. As a result the church more clearly understood and taught her own faith. She learned through the struggle more precisely that Christ was both God and Man in one person, pre-existent eternal God and born of a woman – fully man.
It is good, therefore, that there are divisions to refine and bring about the truth in various forms of bronze, silver and gold, while rejecting the wood, hay and stubble. In this sense the divisions later on started to take the modern day use of them as a negative term indicating ‘heretics’. As the divisions grow and establish, some seem to oppose the very foundations of Christianity so those divisions are called ‘heresies’. However, in the exegesis of this single verse, we can forget that latter concept and ‘end result’ from the negative standpoint and see the higher spiritual and positive value in the divisions themselves as presented by Paul. Actually the churches doctrines are one of those divisions but instead of calling it heresy we call it ‘orthodoxy’. The divisions can be positive or negative.