Why is the U.S.A. not a signatory to the Geneva Convention on the Rights of the Child?

The U.S.A. and Somalia are the only U.N. member states that have not signed the aforesaid document. So far as I can understand this is due to the fact that it would mean that restrictions are applied to home schooling, and that children under the age of 18 cannot be sentenced to life imprisonment without parole. Are there any other reasons?