I believe that explaining to parents how students will actually be using the technology (to engage with content, receive information in a manner that they can understand, demonstrate their knowledge, and receive feedback) and reassuring them that their student will not just sit mindlessly in-front of a screen, can be a strong argument for more screen time. It may also be helpful to mention all of the other activities that do not involve screen time and how the off-line learning can benefit from students engaging with technology.
I would suggest starting the conversation with parents by talking about how you plan to improve the learning experience (e.g. addressing students' individual learning needs, helping students catch up when they are behind, letting students move ahead when they've mastered content, giving students more agency and accountability, providing more timely and helpful feedback, etc.) You could also discuss how not all learning experiences involve screen time and then talk about how screen time complements offline learning.
At Washington Leadership Academy, we've found that 9th grade parents are generally not concerned with screen time. By the time students reach college and career, they may spend most of the days behind a computer screen. High school is practice time. Also, parents are excited that their kids are becoming computer ninjas. We all know how much farther we would be in our own careers if we had more tech skills!