Firstly, it's great to know that students are proactively seeking clarification about commas! All teachers will know that commas are often found sprinkled like pepper throughout students' writing, if at all – and it's no wonder! Commas are one of the most inconsistent punctuation marks. Even professional editors and publishers disagree about where they should be used!
In this article, I'll run through what the National Curriculum (NC) says, and how we've applied that in our activities.
The guidance on commas is quite limited in the NC:
In Year 2, commas to separate lists;
In Year 3, commas to punctuate speech;
In Year 4, after fronted adverbials;
And lastly in Year 5, about the 'Use of commas to clarify meaning or avoid ambiguity'.
Coordinating conjunctions are not mentioned specifically, and are not tested in the SATs. There are some style guides which recommend commas before FANBOYS when joining two independent clauses. We feel this is quite a good habit to help students notice clauses, even if it's not consistent in every text they'll see.
One of the best sites I use for reference when making games is: http://englicious.org/glossary. It is maintained by Bas Aarts, a grammar professor at UCL, who I have chatted to a few times – but even they have very little to say about commas!
There's another interesting article about it here (albeit American English, so take with a pinch of salt! https://www.grammarly.com/blog/coordinating-conjunctions/)
Notice that the header image here includes some FANBOYS conjunctions without commas. This second poster shows how commas between independent clauses can help the flow of meaning and make the content more digestible.
