Denver Public Schools has revised its discipline matrix, which was criticized after last year’s shooting at East High School, but the district stopped short of making significant changes to its guidance on when students should be expelled or suspended, according to a presentation Superintendent Alex Marrero gave the Board of Education on Thursday. District officials began reviewing the matrix, which is a guide for school administrators to use when deciding how to discipline a student, last year before the East shooting, but did further revisions following the incident.