Sight reading is more than the note names, it is also the action of moving your fingers and not just finding the note on the keyboard but keeping your hands in the right position so your others fingers can do what they need to do. So you set your metronome nice and slow and play through your scales while singing the notes and get ear training thrown in for free. Flash cards will just add in an extra step here, you still have to learn those finger movements, sight reading and ear training. Just remember to speed up that metronome when things get easy. The Theory side is much the same.
The single best thing you can do is make practice a part of your daily routine, an hour a day every day. If you are doing that or close to doing that then you need to talk to your teacher about the lack of progress and possibly find a new teacher.