I've seen it happen, but I wouldn't rely on it! There are a few reasons that your score might be different on test day than it was on your practice tests.
your score might be lower on test day if:
- you were taking your practice tests in an inaccurate way (taking too many breaks, eating/drinking during the test, skipping the IR and AWA, etc.)
- you have trouble with test-day nerves
- you try to do something differently for the first time on test day (for instance, you guessed during your practice tests, but feel like you shouldn't guess on test day because it 'counts more')
- you just got unlucky (your score can easily vary by 30 points in either direction at the same level of ability)
your score might be higher on test day if- 'test day magic': many people actually work better in a higher-pressure, higher-stakes environment. You may feel like everything suddenly 'comes together' when you take the real thing, if you're one of these people
- you find it easier to concentrate during the real test than during practice tests, due to the lack of distractions
- you were taking your practice tests under non-ideal circumstances (for instance, if you took your practice tests while exhausted after getting home from work, but you take your official test in the morning after a good night of rest)
- you just got lucky
In short, it could go either way, and it's hard to say which way it'll go until you actually finish your official test. If you're pretty close to your goal score on practice tests, though, I'd go ahead and take the official test, even if you're not 100% confident that you'll get there. You may very well squeeze out a few extra points on test day. But I wouldn't assume that you're going to see a 50+ point improvement on the official test, either.
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