According to a new study, if first borns have better IQs than their siblings and perform better in school, it’s because of their parents. First children get the best parenting and therefore the best grades.

Below is a list of the main theories why first kids would be smarter than their brothers and sisters:

1) The Divided-Attention Theory.

2) The Bad-Genes Theory.

3) The I’ve-Had-It-With-Kids! Theory.

4) The No-One-to-Teach Theory.

5) The Divorce Theory.

6) The Lazy-Parent Theory.