Complex sentence: The first time the band played together was in 1998, when the members were still in middle school, however, they didn't officially form Sand Section until Gonella and Nisen were upperclassmen at UC Santa Cruz and UC Santa Barbara respectively.
Split into simpler sentences: The first time the band played together was in 1998, when the members were still in middle school. However, they didn't officially form Sand Section until Gonella and Nisen were upperclassmen at UC Santa Cruz and UC Santa Barbara respectively.