[Closed] Sram changer with Shimano rear mech - does it work?

As per the title. Its for my son, the 1:1 of the sram changer would be an upgrade from the Shimano as its a big stretch for small hands and the thumbs only would be an improvement (I hope!). But would the indexing work or do I need a new rear mech? I know the front end works as that is what I run on my bike.

Paul.