About 300 students at a Long Beach high school are exploring ways to make their community environmentally sustainable and preparing to share what they learned at a youth summit later this month. On their own, students ranging from freshmen to seniors at Cabrillo High School approached teachers a while back about researching ways to stretch water supplies in drought-prone Southern California and to combat climate change locally. “The project is basically student driven,” said Karen Shoop, an English teacher at Cabrillo High who has helped with the project. “Instead of it being a top-down from the district to the teachers to the students, ‘Hey, guess what, we’re assigning this,’ it was a, ‘We’re interested in doing this research. How do we make this happen?’” she…