Closing the Gap 2016 report from the UK involved a random trial of several intervention programmes for Maths as well as Literacy and the style of teaching. The research aimed to find which programme was the most effective and the students' learning sustained.
In summary:
FSM - Students entitled to a Full School Meal grant
To read the full report, Click here
Many schools, individuals and RTLB's have also researched the effectiveness of NIP in New Zealand. You can find these through university research links.