) That's my opinion, others may say that in the second sentence "he ran past" is ellipted in phrases "round the corner" and "onto the school allotment" thus making the sentence the compound one. Also, it may be argued that the "cobwebs dangling down and dust settling" are non-finite subordinate clauses (complements in the prepositional phrase "with cobwebs dangling down and dust settling") thus making the sentence the complex one.
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