Educationally subnormal means bad quality of education.
What is educationally subnormal?
Educationally Subnormal is a condition diagnosed before age 18 that includes below-average general intellectual function, and a lack of the skills necessary for daily living.
Children described as educationally subnormal will be intellectually impaired in either a moderate (M) or severe (S) form. Many ESN children will have associated disorders in areas of physical and emotional development.