Why was it a crime to teach slaves to read and

Because back then white people didn't want black people to learn anything and trust me I'm black but I'm not that old they didn't want to get over-run and killed and ruled by black people so they made us stay stupid and their rule and they were rich, smart and living in nice big houses.

It was considered a crime to teach slaves to read and write because they worried that if they could communicate privately, then they may have formed plans to escape. It would have heavily damaged the selling of slaves, and would have also hurt the economy. At that time, much of the economy depended on slave trade for money. If slaves could devise plans to escape with each other secretly, then that would also have made slave masters lose much of their money since slaves were not cheap. 

Have a good day! :)