It would roll out so that current Year 8 and 9 "enrichment" classes would continue through to Year 10.
There was "full support" from staff and Board of Trustees with the decision confirmed last night.
An email proposing phasing out streaming was sent to the school community in late September, requesting feedback from parents and guardians through an online survey.
Walsh said there was no "strong evidence" that streaming benefitted any students - including top academic performers.
"The research is however unequivocal that streaming can have significant and adverse impacts on learners including low self-esteem, narrow educational pathways, unhealthy competition and lost lifetime opportunities."
And negative impacts of streaming were "amplified" and "long-lasting" for Māori and Pasifika learners.
"This is inconsistent with our Catholic worldview and commitment to being culturally inclusive.
"All of our students including the top academic achievers will continue to receive an educational programme suited to their needs and aspirations."
Walsh encouraged other schools to review the research and consult their communities about class streaming.
Board of Trustees deputy chair Jenny Chapman said it was "wonderful" to be part of a change in education that was research-based.
The school senior leaders had been carrying out a "concerted and focussed" investigation into steaming for the past two years.
"I am absolutely all for it. We don't need to rely on an old system of separating students out."
And she said it was important to keep in mind what was best for Māori learners.
"John Paul College is thriving to be a Te Tiriti o Waitangi led school.
"We want to create a community where students are exposed to other students from all different backgrounds and abilities - and they are sharing that knowledge together.
She said assistant principal Stephen Bloomfield would ensure the "change over is smooth", checking in with parents who had concerns about the decision on an ongoing basis.
She said out of those surveyed, 80 per cent of respondents were "absolutely" in support of the phase-out.
"It was very well engaged with."