Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| School Name | City | Grades | Establishment | Charter |
| --- | --- | --- | --- | --- |
| Aliamanu Intermediate School | Honolulu | 7-8 | 1958 |  |
| Anuenue School | Honolulu | K-12 | 1958 | Charter |
| Central Middle School | Honolulu | 6-8 | 1926 |  |
| Dole Middle School | Honolulu | 6-8 | 1955 |  |
| Halau Ku Mana NCPCS | Honolulu | 6-12 | 2000 | charter |
| Jarrett Middle School | Honolulu | 6-8 | 1955 |  |
| Kaimuki Middle School | Honolulu | 6-8 | 1939 |  |
| Kalakaua Middle School | Honolulu | 6-8 | 1928 |  |
| Kawananakoa Middle School | Honolulu | 6-8 | 1927 |  |
| Moanalua Middle School | Honolulu | 7-8 | 1967 |  |
| Niu Valley Middle School | Honolulu | 6-8 | 1955 |  |
| Stevenson Middle School | Honolulu | 6-8 | 1937 |  |
| Washington Middle School | Honolulu | 6-8 | 1854 |  |
Question:
how many schools were established before 1955?
Answer:
6