50 synonyms suitable for children in 3rd and 4th grade:

 

1. Big - Large

2. Small - Little

3. Happy - Joyful

4. Sad - Unhappy

5. Fast - Quick

6. Slow - Sluggish

7. Smart - Intelligent

8. Funny - Hilarious

9. Scared - Afraid

10. Brave - Courageous

11. Nice - Kind

12. Mean - Unkind

13. Bright - Shiny

14. Dark - Dim

15. Tired - Exhausted

16. Hungry - Starving

17. Full - Satisfied

18. Old - Elderly

19. New - Fresh

20. Quiet - Silent

21. Loud - Noisy

22. Hard - Difficult

23. Easy - Simple

24. Happy - Content

25. Sad - Gloomy

26. Big - Huge

27. Small - Tiny

28. Hot - Warm

29. Cold - Chilly

30. Sweet - Sugary

31. Sour - Tart

32. Kind - Gentle

33. Brave - Fearless

34. Bright - Luminous

35. Shy - Timid

36. Brave - Bold

37. Fast - Swift

38. Slow - Leisurely

39. Tasty - Delicious

40. Yummy - Delectable

41. Funny - Amusing

42. Smart - Clever

43. Happy - Delighted

44. Sad - Melancholy

45. Kind - Nice

46. Brave - Valiant

47. Fast - Rapid

48. Slow - Gradual

49. Loud - Boisterous

50. Quiet - Peaceful