I think using top level junior sides as a reference is a bad idea since, for example, here Level 3's will referee the U21's of professional football, I doubt Norway has that kind of quality officials refereeing their professional U21's.
Level 9's are referees who have attended the FA Referees course but not yet completed their first 5 games and passed their referee examination. Once the 5 games are done and they must pass an examination, if they're under 16 years of age they move to Level 8 and if they're 16 or over they move to Level 7. Level 7's are capable of refereeing standard low level Saturday/Sunday league football. To become a Level 6 referee, they must pass another examination and achieve the necessary standard of performance when assessed on a minimum of 3 occasions. Level 6 is pretty much no different. To become a Level 5 referee, they must pass another examination and achieve the necessary standard of performance when assessed on a minimum of 3 occasions and act as an assistant referee at the highest level of amateur football on at least 5 occasions. The difference at Level 5 is negligible apart from being able to referee some semi-pro U19 sides and being appointed to ass. There is no fitness test for levels 5-9.
To referee at Level 4, you must achieve the necessary standard of performance when assessed on a minimum of 3 occasions and pass a fitness test. This requires a 12 minute continuous run during which you must complete the minimum of 2600m, before completing 2x50m sprints in 7.5 seconds or less. Level 4 is the first step where referees are handled by the national FA. They referee on the first step of the non-league ladder, essentially regional football. They assist at a level where the country is basically split into thirds.
Level 3's referee at the level where the country is split into thirds, and generally assist on the Conference North/South or Prem. It gets complicated here as there are bandings within the level. If I'm not mistaken the higher band allows them to assist on the Football League.
Level 2's referee on the Conference North/South and Prem banding dependent and would usually assist on either the Premier League or Football League.
Level 1's referee on either the Premier League or Football League.
I'm aware, before anyone says it, that some of the above is generic and I could have gone into all the bandings, but I feel that's the level of information he needed. A basic, rough understanding of the levels.