The absolute best argument against socialism for students is the shared-grade example. Tell them that their grades will be reduced - say, from an A to a B - to bring up the grade of someone else. Then next test, the A's will get a C so that more students that didn't study get better grades. Oh and make the subject the one they want to make a living at. This is done in a few colleges to demonstrate the income redistribution agenda of taxation, and the students are surprised at the analogy.
This is to me a naive example of socialism, mainly because it assumes that 'grades' are the entire point of schooling. Of course, one isn't in school to get some 'grades', one is in school to get an education.
So a socialized approach might be to pair the strongest of students up with the weaker students on projects in hopes that the weaker students would learn from their peers. The upside is that the weaker students might get a better education and the stonger students might as well (teaching is often the best tool for learning). The downside might be that the stronger students simply carry the weaker ones and do all the work.
There are advantages and disadvantages to all approaches, but to simply label a socialistic approach as one of 'grade' redistribution is very simplistic and misleading. Then again, this isn't too surprising as people love to slap labels on complex ideas that overly simplify them. Does anyone think that Joe McCarthy was interested in the actual political views of the people he blacklisted as 'communists' or was that just a label?