I've lost the ability to focus

Hey don't get yourself down about it, I'm sure your interviews went better than you thought, the stressful environment of interviews can often make you feel like you did badly, but people find that they are then pleasantly suprised. Also remember that they aren't the be all and end all and that there are always other ways and routes theiugh life than wht you expected. For the schoolwork side of things,try talking to a teacher or someone at school and maybe ask for an extension to complete work, or a few days off to allow you to reset and get on top of things. Perhaps you could talk to a school councillor if you have one to see if they have ny recommendations. Maybe the school are setting to much over lockdown- mine certainly were and we all told the school so they relaxed it a bit- and you could get together a group of people and tell them that?
I find I can't concentrate well, particularly during the pandemic and lockdown- hence why I'm scrolling on studentroom instead of working, I find that working for short bursts and then having a short break work well, as it means that the work you do is when you are as focussed as possible.
I'm sorry if this isn't helpful, but just hang on in there and I hope things get better for you- you've got this and I'm rooting for you.