childhood一般不用复数形式,有定语修饰时,可加不定冠词。指孩提时代的教育、环境时，可以有复数。

They have been good friends since childhood.他们从小就是好朋友。
He had a happy childhood in the country.他在农村度过了幸福的童年。
Are we what our childhoods made us?我们今天的一切都是孩提时代所培养成的吗?