my 3 year old also started kindergarten last year and is now finally settling in. she also used to cry a lot, but this is very normal, as all kids go through separation anxiety. different babies have different ways to deal with it. however,you have to be strong as a parent and not give in to those tears, which i know can break anyone's heart.
here are a few articles i found really useful, so sharing them
http://www.scholastic.com/browse/article.jsp?id=1372
http://kidshealth.org/en/parents/adjust-to-preschool.html
https://www.scholastic.com/teachers/articles/teaching-content/ages-stages-how-children-adjust-school/
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