Student visa request was disapproved based on 126 (b) of INA. How can I learn the exact reason?

Me (32) and my husband (37) with 2 kids (3 and 5) requested a student visa for a 1 year English learning program. My parents living in US would have ensured our accommodation. I sufficiently proved that English proficiency is advantageous in my job (I'm a special teacher and after my return I could teach English for pupils with learning disabilities). Me and my husband have several years employment and relatives in our country. We own 4 real properties and 2 cars. We visited my parents last December with ESTA, and returned to our country after 3 weeks. My questions: how can we learn the weak points of our application? how could we prove better our ties to our country? does it help if we shorten the period to 8 months in our reapplication? Thank you!