COTTAGE GROVE, Minn. — Adjusting bell times from four tiers to three tiers is among transportation changes that are under consideration at South Washington County Schools.

Officials said that since a change in school start times for the 2009-10 school year, the district’s transportation department has struggled to provide on-time service in the afternoon to numerous elementary schools that fall in the 8:10 a.m. to 2:40 p.m. tier in the four-tier bell time schedule.

In recent years, the district has contracted for 10 to 12 additional buses. Yet even with that addition, many buses are still running late at the end of the school day.

Under a new proposal to switch from the four-tier bell schedule to three tiers, the 8:10 a.m. start time tier would be eliminated, which would affect 10 elementary schools. Two of those schools would start 15 minutes earlier, while the other eight would start 30 minutes later. All other South Washington County schools would keep their current start and end times.

“The proposal provides efficient service for both morning and afternoon routes,” according to an announcement on the district’s website. “Middle school students would be dropped off at school closer to the start of the school day than the existing 30 minutes.”

Reducing the number of tiers would also increase the number of buses required. A total of 10 contracted buses in the morning and 10 contracted buses in the afternoon would be needed to serve two school buildings.

This would be an increase in contracted services over the 10 to 12 buses that have been contracted for the afternoon only. However, South Washington County Schools officials said that the total number of buses required in-house would be reduced from 95 to 94 in the morning and from 100 to 94 in the afternoon.

The additional cost of the three-tier proposal would be $50,050.

Another change being considered for transportation service would be to reduce walking distances from 1.5 miles to 1 mile for middle school students and from 2 to 1.5 miles for high school students. The shorter distances were in place before the current school year, when they were increased as a budget reduction measure.

The cost to revert to the shorter walking distances for the 2014-15 school year is calculated at $143,751.

The district’s transportation service level team said that changing to a three-tier system and reducing the walking distances would significantly increase the level of transportation service.

The proposals were discussed at South Washington County Schools’ Feb. 20 board meeting, and they are on the agenda for the board meeting this Thursday. Also, the start-time proposal will be shared at length with elementary school families at two public meetings set for March 17 and 18.