They are adjectives, modifying courses and kid respectively. "level" is not an adjective, so "higher" is not an adverb "popular" is an adjective, and "most" is the form for the superlative
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Philippopular" is an adjective, and "most" is the form for the superlative
Philip"level" is not an adjective, so "higher" is not an adverbOh really, I thought level was an adjective... So it's a noun then?