There are so many different theories, which you probably know because you are studying this stuff.
Milestones for Children is such a huge topic.
I personally like Piaget's six stages of sensorimotor development for cognitive development from birth to 24 months.
It depends on what your report is focusing on because a combination of theories could be what your teacher/professor is looking for. Piaget's cognitive stages of development and Erikson's psychosocial stages are a good combination if you are spanning through a child' s life.
With both theorists, you would be touching on the cognitive and emotional development of a child's lifespan through adolescence.
Auzzie really did a great job at answering your question in a condensed yet precise, simple way!!! My papers were always too dang wordy. I think it drove my professors crazy.