There is really no such thing as a yellow school.
Look at your next three years' data and you will find out whether you are yellow going on amber or yellow going on green.
If you are going on to amber (ie this is the way your data is going), now is the time to:
strengthen your roles and responsibilities;
make clear where accountabiliy lies;
ensure your data flows are spot on;
identify the changes you need to make;
identify the management changes techniques you need to use;
Why the urgency? Yellow means you still own your school and you can choose who you want to work with. Go down to amber and suddenly the agenda is not yours anymore.
If your data is about to move you to green, it is time to consolidate everything and change these expectations in a set of clear targets. I have never worked with any school that has 'ended-up' green. They are green because they worked very hard at it.
They made sure they had the processes to support their high expectations.