Hello, 

These are the eligibility criteria to become a teacher for elementary as well as upper primary school. 

For elementary:

I.Senior Secondary School certificate or Intermediate or its equivalent with 50 % 
marks; AND
ii. 2 year Diploma in Elementary Education or 4 year Bachelor of Elementary 
Education or 2 year Diploma in Education (Special Education)

For primary:

i. Graduate and 2 year Diploma in Elementary Education 
OR
ii. Graduate with atleast 50% marks and 1 year Bachelor in Education/Special 
Education 
OR
iii. Senior Secondary School certificate or Intermediate or its equivalent with 50% marks 
and 4 year Bachelor in Elementary Education (B.El.Ed)/4 year BA/B.Sc.Ed

To know more about the criteria and as well as the FAQ 's, please go through the following link 

https://www.google.co.in/url?sa=t&source=web&rct=j&url=http://dled.nios.ac.in/DELEDFAQ.pdf&ved=2ahUKEwj-lbeYpcffAhVZVisKHfBOACAQFjAAegQIAhAB&usg=AOvVaw0Cuqod-otTIJIs7KbOZc6z

Hope this helps......