Depends on where you want to put the line of demarcation for levels of a development system, considering it evolves at different ages in different countries, and may vary in different areas of a country.
Canada: minor hockey is the predominant route all the way up through u16 until your CHL/junior draft year. Sport school academies have become popular in Western Canada, the GTHL reigns supreme in Ontario. Not quite sure how it all breaks down in Quebec. Major junior in the CHL is great for talented 16 and 17 year olds, but can be redundant for 18 and 19 year olds who need to be challenged more and are held back due to the CHL-NHL Agreement, so thus they can't play in the A. Junior A in Canada is all over the place now with the BCHL going independent and the turmoil in the AJHL, so many top NCAA route Canadians leave the country to play in the USHL now.
US: Varies depending on where you're at in the country. Community based hockey & then high school reigns supreme in Minnesota, minor hockey to prep school is the typical route in Massachusetts & New England, minor hockey is the top route in Michigan. Prep school and high school hockey do exist in other parts of the country, but minor hockey is necessary everywhere else because the talent pool isn't deep like it is in Minnesota, thus the need for minor hockey organizations to group the best talent together.
After that, the NTDP is the junior all-star team for the best US NCAA route players, the USHL has gotten better & better as a junior league, but it's still hard for most non-NTDP players to get big minutes in the USHL in their 16 & 17 year old seasons, as the USHL is still used as a developmental parking spot league for NCAA programs to put their recruits in so they can stagger recruiting classes and then bring in guys as older players. And then the NCAA has become an even better 18-24 year old league, allowing top 18 and 19 year olds to play against older competition when they've outgrown junior, but it also allows later bloomers a longer development curve on the path to making it to pro.