Power Pivot: Average by group using many-to-many table relationship - excel

Question

I have three tables in Power Pivot. Pupils, Baselines and Reports. The Pupils table connects to the Reports and Baselines tables via a One to Many relationship as shown below.
The Reports table has each pupil listed multiple times for each subject they have a report in. They are also listed multiple times in the Baselines table for each baseline score they have. What I want to accomplish is to create a measure that calculates the average baseline score in each subject. So take all pupils who have a maths report, I want to know the average baseline score in maths.
I tried the following measure:
Av Baseline:=AVERAGEX( CALCULATETABLE( Baselines, Baselines[Type] = "Overall" ), Baselines[Average] )
However the above when used in a pivot table produces the same result for all subjects, so the filter context is not being applied. I keep hearing people using bridge tables, which does add a ton of data and are not very efficient so I hope to avoid those if at all possible.
I have provided some example data with the desired output table, hope that helps?

Answer 1

Could you please test this:
Note: I hope Your Pupils table has a column called [Subject Code] It is not clear from your shared data.
Version - 1
Av Baseline :=
AVERAGEX (
VALUES ( Pupils[Subject Code] ),
CALCULATE (
SUM ( Baselines[Average] ),
CALCULATETABLE ( Baselines, Baselines[Type] = "Overall" )
)
)
Version - 2
Av Baseline =
VAR Combin =
SUMMARIZE (
Baselines,
Baselines[Type],
Pupils[Subject Code],
Baselines[Result]
)
VAR Combinfiltered =
FILTER ( Combin, Baselines[Type] = "Overall" )
VAR Result =
CALCULATE ( AVERAGE ( Baselines[Result] ), Combinfiltered )
RETURN
Result