Answer:
The supporting evidence the writer give to convince readers that teens "aren't being tested consistently or thoroughly" are:
1. 35% of the 459 high school seniors were actually tested on just 7 or less of the 12 driving skills which the state police testers are supposed to check. 41% affirmed they were tested on 10 or more.
2. 56% of the students said their test actually lasted for 10 minutes or less but only 15% said theirs lasted for over 20 minutes.
3. 21% of them said their driving school is "fair" or "poor" while 24% said their is excellent.
Explanation:
From the above answer which we see from the passage, we discover that the writer gave statistical evidence in order to support his claim that teens "aren't being tested consistently or thoroughly".
From the evidences given by the writer, one can deduce that the testing process is not actually consistent and thorough. There seems to be disparity among the students - some seem to have good experience while others don't really have. These can be seen from the evidence provided by the writer.
