Maths or Science?

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Across
  1. 6. A tiny mix of biology and maths? (4, 8)
  2. 8. Maths-speak for how often (9)
  3. 9. Nasty average (4)
  4. 12. Can't wear these trousers to school (5)
  5. 13. Special times in Physics (7)
  6. 15. What 7 did to 9 in this period (5)
  7. 16. This pulls you down (7)
  8. 19. Energetic way to get about (6,9)
  9. 21. Everyone prefers this subject (5)
  10. 22. Gone but not forgotten (10)
  11. 23. Tasks completed (4, 4)
Down
  1. 1. In favour of adolescence (7)
  2. 2. Quizzes in Science Support? (2,6,5)
  3. 3. These affairs are happening now (7)
  4. 4. 16 across is a type of this (5)
  5. 5. Mathematical food (2)
  6. 7. An occasional desk? (8, 5)
  7. 10. Liquid asked for in Maths questions (8)
  8. 11. Sounds like this protective layer belongs to a neuro club (8)
  9. 14. Physical reluctance? (10)
  10. 17. This one doesn't sew unlike 22 across(6)
  11. 18. Part of a knee minus a musical term
  12. 20. This vessel likes how it looks (4)