The article certainly doesn't make it sound like they let in anyone:
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Last year, 70,000 people attempted the online qualification test. 20,000 completed the test, and of those, 4,000 were invited to spend four weeks in Paris doing an intensive project that had them working upwards of 100 hours a week on various coding challenges. In the end, 890 students were selected for the school’s inaugural class, which began in November, 2013.
"""
French here who know a few people from 42. The tests to get in 42 are very basic and they're more about testing your patience than anything else. However, in order to get in the other top schools on this list, you need very high grades in math and physics among other things from high school. 42 let people in that haven't even finished high school. Not comparable. The reason they get 70000 people applying is because it's free, most applicants don't even finish the whole test (it lasts many days).
The real test is the pool, not the internet test.
Learning up to binary trees in a month in c with no experience in programming at all ain't nothing like very basic
""" Last year, 70,000 people attempted the online qualification test. 20,000 completed the test, and of those, 4,000 were invited to spend four weeks in Paris doing an intensive project that had them working upwards of 100 hours a week on various coding challenges. In the end, 890 students were selected for the school’s inaugural class, which began in November, 2013. """