I'm unsure of this ko sentence. What's the point of the あげた at the end? I'm not understanding sentences that use two verbs at the end such as this.

子供に昔話を聞かせてあげたの。

Thank you.

上げる, くれる, and もらう can be used as auxiliary verbs after Vte (te-form of a verb) in order to express the idea "do something for someone", "someone did something for me", and "I had someone do something for me", respectively.

E.g.:

本を買って上げた。 I bought a book for you.
本を買ってくれた。 He bought a book for me.
本を買ってもらった。 I had him buy a book for me./He bought a book for me.

Auxiliary もらう has two different nuances which are differentiated by context.

Hope this helps