I surfed the internet to find articles on disengaged students and here is an extract from one of many articles. All the ones I read had similar points of view but none had the main reason why kids disengage from learning to read.
The following is an excerpt from the e-booklet Working with
children who are disengaged and unmotivated in the classroom by Zoe Ganim and
Murray Evely. You may read the whole article here.
Children who are motivated to learn generally attend school regularly, do better academically and display pro-social classroom behaviour. Unfortunately, up to 20 per cent of students in any year are described as disengaged.  Many do not catch up academically in later years.
My comment: I believe that the 20% of students described as disengaged are also motivated just like all the others children when they first go to school. There is no lack of motivation in most of these children. They shut down/ disengage from learning to read when they are confused as a result of wrong teaching.
Some students who are disengaged or lacking motivation may hide learning difficulties or giftedness to fit in with peers.
My comment: They don’t lack motivation but are disengaged because what is being taught does not make sense to them. It is wrong to say that they have a learning difficulty. They don’t have a learning difficulty as almost all of these kids can be brought to grade level and maintained at grade level with a short period of intervention as stated by Dr. David Kilpatrick in his books.
Disengaged students are not necessarily unmotivated to achieve in all subjects.
My comment: Yes, I have said this numerous times. Most of them do not have a problem with mathematics in which they are usually top students. Most of these students have a problem with reading only in English but not in other languages.
Teachers tend to attribute unproductive classroom behaviour to the student and non-school related factors (home life, socio-economic, cultural, religious, health, trauma or personal relationships). Non-school-related factors can be difficult to change quickly. While they undoubtedly influence levels of motivation, they are only one of many issues affecting student engagement in the classroom.
My comment: True. Shame avoidance is the main reason for misbehavior.