Entendo que se trata de um festival aberto aos alunos secundários de TODAS as escolas do Estado em foco.

Entendo que seja um festival onde todos no estado participam, por exemplo, todas as escolas do estado.

The Vermont All State Music Festival is an annual event supported by the Vermont Music Educators Association (VMEA) and operated by the Vermont All State Committee. The Festival offers musicians from Vermont's high schools the opportunity to perform in a band, orchestra, chorus or jazz ensemble under the direction of some of our nation's finest conductors. Three days of intensive rehearsals lead up to a series of performances involving all four groups.
http://www.vmea.org/allstate.html