In the UK most learners start out doing SkateUK which has 10 grades.
See here for info. Some rinks have their own scheme instead. My rink follows SkateUK levels about 95% of the time but instead of some of the easier parts of the higher grades, introduces a few higher level skills that will be needed for passport or field moves later on instead.
After SkateUK or equivalent you move on to "Skate UK Star - Passport to Competitive Skating", often called Passport. There are 4 streams - Singles, Ice Dance, Syncro and short track speed. Each stream has 3 parts - Bronze, Silver and Gold.
See here for info. Passport is assessed by your coach.
Some things in passport come up again in subsequent tests so are held to a lowish standard to pass passport, eg jumps - Waltz, Salchow and toe-loop are in singles passport but crop up again in Level 1 and 2 in the NISA national tests where they are expected to be much better in order to pass each different level.
Once you have passed passport you can then take NISA national tests in
... singles you can go on to test - field moves, free and elements.
... ice dance you can go on to test - field moves, pattern dance, Variation/Origional dance and free dance.
There is also a set of Pairs tests but I'm not sure what is required for those.
There is no info on NISA national tests on the NISA website but wikipedia gives a
brief overview of all the later tests. There are stupid number of them! A link to
the test application paper pdf shows exactly how many! Some higher level tests can be passed as IJS competitive tests instead.