Read this text, taken from a site named My Read: Strategies for teaching reading in the middle years, which supports teachers of underperforming students.      All students can be successful readers    Reading is a complex and challenging process. Yet for all but the 5 - 10% of students who have intellectual, sensory or learning disabilities the issue is one of underperformance rather than ability. For the majority of students reaching the middle years of school, recurrent experience of failure and negative perceptions about themselves as readers will be major obstacles to learning. For these students, performance in reading is likely to be a consequence of a well-learned selfpreservation strategy of non-engagement. 
Underperforming middle years readers must first be motivated to engage and re-engage with texts. Specific reading skills can only develop as an outcome of that engagement. Engagement is an interactive process. It requires teachers to have a close knowledge of students and their reading, and so be able both to provide sufficiently challenging learning experiences as well as the necessary support for those experiences to ensure successful learning. Student engagement can only occur as they recognise that they can be successful partners in this process. 
(http://www.myread.org/BELIEFS.HTM. Accessed on March 2nd, 2013.) 
Read the sentence: “It requires teachers to have a close knowledge of students and their reading, and so be able both to provide sufficiently challenging learning experiences as well as the necessary support for those experiences to ensure successful learning.” The pronoun ‘their’ here refers to