Which is correct? was or were. I think this might be subjunctive
If safety of students was/were the primary purpose of schools [which it isn't], educational opportunities would be severly different: There would be no playgrounds, no science experiments, no spots, no marching bands.
The subjunctive form were is preferred by many, especially in AmE. Many people would use was in BrE.
Context is always important; labelling is rarely important.
Well, that's the confusing thing about the subjunctive. After "if" (for example"), the word "were" is used for all six persons.
If I were ...
If you were ...
If he/she/it were ...
If we were ...
If you were ...
If they were ...
As you can see, it makes no difference whether it's singular or plural. Yes, "the welfare [of students]" is a singular noun, but in the subjunctive takes "were", as do all the others.
So, as 5jj said, the subjunctive is preferred by some people but has certainly fallen out of usage with a lot of people. I would expect to hear "If ... was" from the majority of BrE speakers under about 30, and from quite a few over 30, these days. As far as I know, it's no longer considered to be incorrect. However, "If ... were" is never considered to be incorrect.