In this blogpost we’re going to tackle a difficult question [1]: whether having an EHC plan can prevent exclusion and repeat suspension.
The challenge in answering it is one of what economists call selection. The factors that lead to some pupils having EHC plans and others not may be related to the propensity to be excluded. If EHC plans were handed out at random, as they would be in a randomized controlled trial, for example, this would not be a problem. But an RCT of EHC plans is never going to happen.
So what we have to do is try our best with existing data. We do this using an approach known as Instrumental Variables (IV).
This involves finding another variable which increases the probability of receiving an EHC plan but should not otherwise affect the outcome of interest, in this case exclusion.
