I can't concentrate on homework when i have to do it online. how can i become more efficient?

Concentrate: Evaluation for add might be worth while, especially if easily distractable and school work deteriorating.

Different strategies: Try different homework strategies. Try studying all at once if you can sit there for the necessary period of time. Or take breaks for a few minutes every half hour to rest your brain. Or take a more substantial break once during your study session to have a meal or exercise or call a friend. You need to find the strategy that works for you, allows you to get everything done and get good grades