Jersey's education system needs to be "radically simplified" in its funding to "deliver a good education for all students", an independent report found.
The current financial position is "unsustainable" and "rapidly deteriorating", it found.
It said an annual funding shortfall of £2.4m was "most acute for disadvantaged children".
The Government Plan, which has yet to be approved, suggests an initial £7.9m investment rising to £11.6m.
The report, from management consultancy The PSC (formerly 2020 Delivery), recommends targeting additional funding at schools where students have the most significant special educational needs.
It said £8.5m was needed immediately to "stabilise current provision" and make initial improvements.
Other immediate recommendations include a radically simplified funding formula, forming a Teaching Excellence Fund and greater collaboration between schools.
It also called for stronger governance and greater financial autonomy for schools as a priority.
Jersey has 42 schools, catering for 15,000 children, and the report recommends some mergers between establishments.
The report looked at high performing education systems and found funding per pupil in Jersey was significantly lower for primary, and similar for secondary.
The report said "becoming a world-leading education system is a journey likely to take more than 10 years and international experience shows successful reforms go through multiple distinct phases".
Education Minister Senator Tracey Vallois said: "These recommendations represent significant changes.
"Delivery will take time however, consideration and assessment for their impact will have to be carefully managed and some options suggested will need appropriate consultation".