1. Sientate (singular) / Sientense (plural), por favor – Sit down, please
2. Ven aqui (sing.) / Vengan aqui (pl.) – Come here
3. Despacio – Slowly
4. Basta ya! (sing.) / Dejarlo ya! (pl.) - Stop doing that!
5. No hagas asi! (sing.) / No hagais asi! (pl.) – Don’t do that!
6. Basta! – Stop at once!
7. Rapido! Moveros! Enseguida! Muevete! (sing.) / Muevanse! (pl.) - Quickly! Move! Hurry!
8. Callate (sing.) / Callaros (pl.) – Quiet
9. Atencion! Cuidado! Escucha (sing.) / Escuchen (pl.) - Be careful (it can be used to get children to pay attention)
10. Sucio (sing.) / Sucios (pl.) - Dirty
11. Limpio – Clean (adjective)
12. Limpia (sing.) / Limpiar (pl.) – Clean (verb)
13. Desordenado – Messy
14. Borra, tacha – Erase
15. Repite (sing.) / Repiten (pl.) - Redo, repeat
16. Bueno, esta bien – Good or well done. Muy bien - Very good. Estupendamente – Excellent
17. Educado (sing.) / Educados (pl.) – Polite
18. No – No
19. Si – Yes
20. Gracias – Thank you
21. Buenos dias – Good morning
22. Maestra (fem.) / Maestro (male) - Teacher
23. Hagan un circulo – Form a circle
24. Hagan una fila - Form a line

Also: See Spanish lessons (with over 100 audios) at:
http://www.eslteachersboard.com/language/spanish/spanishlesson.htm