The incorrect use of punctuation speaks volumes to your audience. When a sentence is structured incorrectly, you are broadcasting several things to your readers. First, it's obvious that you did not learn what you were supposed to in school. And second, you don't care about what you are writing. This doesn't send a good message. And you may have wasted your time writing, since few people will pay attention to poorly written text.
Consider advertizing, job profiles, letters from friends... What have you remembered from experiences involving terrible punctuation? Not much of the subject matter I expect.
Your compositions are like a canvas. You are creating a small work of art, and using that to convince readers that you are intelligent. You should never allow your audience to read sub-standard work. It gives them the chance to doubt that intelligence.
This does not mean using longer sentences or fancy words. It is about structure, flow, good grammar and proper spelling. And when complex thoughts are to be written in a small space, they must be clear and flow properly.
get a web page!
Everyone knows that a period goes at the end of a sentence. That's the easy one. Colons and semi-colons are more complex but really have no place in this discussion since this site is about preparing young writers. It's the wandering comma that needs to be understood. It can have devastating effects on the written word when used incorrectly or not at all.
The comma breaks a sentence into small thoughts and encourages the reader to insert a brief pause. If the comma is missing, or if one is inserted in the wrong position, the sentence may lose its meaning. Worse, a sentence with incorrect punctuation can take on alternate meanings.
Here is the classic example to illustrate the point (I know it includes a colon)...
This sentence, provided to a group of adults, reads "A woman without her man is nothing"
It can be punctuated like this... "A woman, without her man, is nothing." Surely a male perspective.
Or like this... "A woman: without her, man is nothing." Obviously a few women in the crowd.
Silly but effective, with totally different meanings. In general, when sentences run on, you should attempt to break them into separate sentences. Everyday readers don't like run-on sentences. If that won't work, then try to find the smaller thoughts, the qualifiers so to speak, and surround them with commas. As in the previous sentence, a qualifier doesn't get just one comma, but two.
Begin to guide your children in good sentence structure. Working on their own pieces will be a good way to keep their