Using full stops and capital letters to demarcate sentences is a requirement of the 2014 National Curriculum from Y1 onward. The following activities have been devised by teachers for working with the youngest children in school but they may still be useful to teachers working with older children who continue to struggle with demarcating sentences accurately.
Use strips of paper to create human sentences with children. Say a sentence, write the sentence, cut-up the sentence and then give separate words to different children so that they can then work collaboratively to recreate the sentence. Use the capital letter and full stop as clues to work out where different words go in the sentence. Over time this game can be repeated with the omission of the capital letter and full stop for children so that children can activate their own understanding to punctuate the sentence accurately.
Tennis ball full stop
Use a tennis ball or other small ball to mark the end of the sentence when building human sentences as a class.
Create actions and sound effects for full stops. Use these actions and sound effects when reading text as a class. Encourage children to use them to decide which punctuation marks to use when reading unpunctuated sentences.