The correct option is C Took part
The paragraph refers to the action already completed. This is simple past tense.
"Takes part" is present tense. This is incorrect.
"Taking part" is the continuous form of the verb. This is incorrect.
"Took part" in option C is correct. This refers to the verb in its past participle form. The verb is also plural, so it is in subject verb agreement with the plural 'schools'.
"Taken part" is in perfect tense. This is incorrect.
Thus, option C is the correct answer.