There are various English tests for children in Japan. Eiken is the most well known test. There is also Eiken Junior, JET, TOEFL Junior.
I want to recommend Cambridge Young Learners Tests. They have 3 Levels:
STARTERS, MOVERS, and FLYERS.
It’s difficult to compare, but as a rough guide:
STARTERS TEST = Eiken Grade 5
MOVERS TEST = Eiken Grade 4/3
FLYERS TEST = Eiken Grade Pre-2
In these tests, there is LISTENING, READING, and SPEAKING.
Children can do a 1 to 1 speaking test with an examiner.
The tests are colourful, interesting for children, and boost motivation.
There is no pass or fail, but you can get a score in each section.