one thing you could try is making a bunch of sentences that use each. then, split the sentences at each occurrence of 'so' or 'so that' and write each half of the sentence on a card. so, for each each sentence, you'll have 3 cards: the beginning, the 'so' part and then end.
Example:
I ate dinner so I was full.
I went to the movies so that I could watch Titanic.
Make the following cards. This is 1 set. You'll need to make duplicate copies of each set for the number of students or teams of students in your class.
- I ate dinner
- so
- I was full.
- I went to the movies
- so that
- I could watch Titanic.
Don't forget to put in the punctuation to help guide your students.
Then distribute the set of cards, 1 set to each group or child or team, however you want to break them up.
Then you will have them make the sentences by putting the cards back into proper sentences. You could do it as a race or just as an activity.
i hope that helps,
eric