I struggle with understanding when to use an apostrophe with singular words ending with S..

Like for example, Class or Hughes.. Would it be Class's or Class'.... Hughes's or Hughes'?

Both are correct. Old rules said to add the extra S, as in "class's" but now it is acceptable not to do so, as in "class'" Rules change over time. I like the old way: add the extra S.

I always teach students to put that extra s in there when you can hear the two s's when you pronounce the possessive.

class's (you should be able to hear it)
This is the reading class's lunchtime.

Hughes' (you don't hear the extra s)
That was Howard Hughes' tool company.

Understanding when to use an apostrophe with singular words ending in S can be confusing, but there are some general rules to follow.

When a singular word ends in S, there are two accepted ways to form the possessive:

1. Add an apostrophe followed by an S ('s): This is the most common and widely accepted way to indicate possession for singular nouns, even if they end in S. For example:

- Class's (pronounced "class-iz"): This is the possessive form of the noun "Class." So, if you want to talk about something that belongs to a specific class, you would write "Class's." For example, "I borrowed Class's textbook."

- Hughes's (pronounced "hugh-iz"): This is the possessive form of the noun "Hughes." So, if you want to talk about something that belongs to a specific Hughes, you would write "Hughes's." For example, "I went to Hughes's house."

2. Add just an apostrophe ('): This is an alternative form used mainly when the word already ends in an S sound (such as with names that end in "s" or "x"), to avoid repeating the S sound. For example:

- Class' (pronounced "class"): This is an alternative possessive form of the noun "Class." However, it is less common and generally used in formal or stylistic contexts. For example, "I attended the class' meeting."

- Hughes' (pronounced "hughes"): This is an alternative possessive form of the noun "Hughes." Similarly, it is less common and mainly used in formal or stylistic contexts. For example, "I went to Hughes' office."

In summary, both "Class's" and "Class'" are correct, but "Class's" is more commonly used. Similarly, both "Hughes's" and "Hughes'" are correct, but "Hughes's" is more common. The choice between using 's or just ' depends on personal preference and the specific style guide or context you are writing in.