Reducing cover to "only rarely"
What the School Teachers' Pay and Conditions Document says about cover (with NUT Comments)
PRINCIPLES FOR THE PROVISION OF COVER FOR TEACHER ABSENCES (Suffolk NUT)
The "RIG" Guidance on "only rarely cover" (not statutory and not agreed by the NUT)
See page 18 of the NUT's Guide to Conditions of Service
Cover and invigilation
Cover and school visits
Suffolk LA Guidance on PPA and Cover
WAMG Guidance on Cover Supervisors
The situation is complicated and the regulations not always unambiguous, so contact your local NUT Secretary for advice in particular situations.