This paper investigated six to nine year old children's ability to use contractive and possessive apostrophes, the effects of type and token frequency, and the effect of teaching on this ability. Apostrophes provide an interesting opportunity to examine the basis of frequency effects in rule inference, as type and token frequencies dissociate in apostrophes found in children's early reading materials. Teaching effects are now open to inspection as the National Literacy Strategy Framework for Teaching lays down a specific and detailed curriculum and teaching timetable. Results showed that token but not type frequency influenced children's correct use of apostrophes. There were also effects of teaching.