He said that marking exams without knowing students' names, and having teachers discuss and review the grades they give with others, would reduce any possible biases caused by personality.
In the paragraph above, they use a present participle with "having teachers" but did not use a present participle with "review the grades". I'm curious as to why? My first assumption is that its because of the Double-ing Constraint but at the beginning of the sentence they used "knowing"?