Duncan Louttit wrote

The rule about mice that do not appear to be following the line being excluded is unjudgeable. How can the judges decide what constitutes line following if there is no specification?

This rule has caused problems in the past as it is a great advantage to a mouse to overshoot the corners and have a large distance to recover after the corner. The old rule was that the judges could put obstacles (cotton reels was the idea) with their inside edge no less than 13 centimetres from the edge of the line (inside and outside the course) at the points that they thought were most interesting. If the mouse moved one of these obstacles that lap could not be used for scoring.

This is a quantitative measure of the accuracy of the mouse and is easy to judge. Any school can easily test if their mouse performs adequately before the competition and make appropriate changes. The "gap" to aim at is a minimum of 31 centimetres, or nearly twice the gap between maze walls so it is not technically difficult.

Jerry Niman wrote

I like Duncan's suggestion of the cotton reels.