Below is a table showing the scores achieved by students in a mathematics competition across five different schools. Each school's scores represent the average of the top three performing students:
| School | Average Score |
|---|---|
| School A | 75 |
| School B | 85 |
| School C | 90 |
| School D | 80 |
| School E | 88 |
Based on the scores, which school has the highest average score?