Three grade spans ?

Hi~ I'm wondering what the phrase "three grade spans" and "a grade span" refer to in this context.

The three level of education, i.e. elementary school, junior high school, high school ?

To be sorry, it's somewhat long but for your reference, I put the writing below. Any idea would be welcomed. Thank you~

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The larger committee was broken down by instructional levels (elementary Grades K to 6, junior high Grades 7 to 9, and senior high school Grades 10 to 12. Each level had the same subcommittees with areas of focus as indicated in Table 11.1.

(omitted) we recruited volunteers for the taskforce. With a lot of support, we had no trouble forming a committee of 119 individuals that included one school board director, 36 administrators, 64 teachers, nine parents, six students, and three community members. It was decided that I, as the superintendent of schools, would be the chair, and three principals would chair the senior high school team, the junior high school team, and the elementary team. The three taskforce teams were divided into subcommittees to study each of the topics: data, placement procedures, support programs, professional development, and parental involvement. Prior to preparing the taskforce report, these subcommittees met across all three grade spans. This structure allowed the participants to share ideas and concerns across the elementary, junior high, and senior high school levels.

The final report of the taskforce focused on areas of commonality as well as on areas that were specific to a grade span. There were seven overarching recommendations in the taskforce’s final report: