What part of speech is the word 'informed' in this sentence?

The kids are much better informed than I was at their age.

"Informed" is an adjective modified by the adverb "better".

The full analysis goes like this:

"Than" is a preposition with the comparative clause "I was at their age" as its complement. The PP "than I was at their age" is an indirect complement licensed by the comparative expression "better". It's called 'indirect' because although it follows the head adjective, "informed", it is not the head that licenses it, but the comparative expression "better" that modifies the head.

The whole AdjP "much better informed than I was at their age" is then subjective predicative complement of "be"