ns changes the achievement. What a surprise.
A second point: on the decline in US ranking in TIMSS, as we progress from 4th to 12th grade, one very obvious candidate is promoting kids to the next grade when they haven't achieved satisfactory progress. Some teachers I've spoken with recently are required by their districts to give no grade lower than C, and to move students to the next grade regardless of their performance. If we move them on when they aren't prepared, of course they won't do well. If we lower expectations a bit, to balance this, then we have all the students who performed well getting bored and goofing off.
Schools that promote students based on achievement rather than age have a better chance of getting all students to the same endpoint. Some will get there sooner than others. Some will advance in one subject faster than in another subject. But that's OK. It still works.
Why not get rid of grade levels and switch to complexity levels?…