Orchestra page 

Take some time to look at other youth orchestra entries in Wikipedia. 
List of youth orchestras in the United States
Look at some that have clean up notices on them and look at some of the better ones. If you do this you will be better able to judge the content. 

You may use published sources that are not on-line. So long as they are reliable and ultimately verifiable by someone who would take the time to look them up to check the information.

Wikipedia has increased the need for Encyclopedic Value. Older articles that are not verifiable are being removed. The ones that have long standing clean up notices will either be rectified by interested parties or will ultimately be removed. Those notices serve to tell the public that the article does not meet the standards of reliability of an encyclopedic article. 

It appears that the Orchestra has been in existence for 50 plus years. It is not an emergency to get an article published. The heading ==Acclaim== jumps out as promotional. This is puffery and self aggrandizement. The article must be neutral in tone. The references or footnotes must back up statements in the article. for example use a statement such as - The orchestra has been well received by audiences in Country A and City B. Put in the references. the references themselves may be full of congratulatory language but avoid putting in the article. By way of illustration, if a news article from Country A said this is the greatest orchestra in the world and got a five minute standing ovation from the audience, you would use that as reference with regard to the aforementioned statement but would not put that directly in the article. If the article is in a venue brochure it is of little value but if it is in the Country A's leading newspaper then it is of value. Ask yourself, what would make this youth orchestra worthy of mention in an encyclopedia. That critical viewpoint will lead to a better article.