0 points: Blank tiles x 15 (normally only x4)
1 point: E ×12, A ×9, I ×9, O ×8, N ×6, R ×6, T ×6, L ×4, S ×4, U ×4
2 points: D ×4, G ×3
3 points: B ×2, C ×2, M ×2, P ×2
4 points: F ×2, H ×2, V ×2, W ×2, Y ×2
5 points: K ×1
8 points: J ×1, X ×1
10 points: Q ×1, Z ×1
I increased the number of 'blank' tiles (which can be used as any letter but are worth 0 points) to 15 as they are exciting for the students and make the game more interesting (I also drew stars on them because kids love that kind of thing).
I split the students into groups of 8 to 10 and give each student one tile. Using their tiles as a team they try and make a word (just 1 word) that has the most points possible (1+3+2+1+8 = 15, you get the idea).
I give them a few minutes to think about it before asking for their words (keeping track of the points on the whiteboard).
After each round I take the tiles the team used to make their word and replace them with new ones. For example if their word was 'CAT', they get 3+1+1 = 5 points and I take the letters C, A and T and give them 3 new tiles to work with.
They can also choose to change all their tiles for new ones at any stage of the game, with the downside being that they get 0 points for that round (not usually worth it but if they're really unhappy with their letters then it gives them an option).
I usually get through around 5 or 6 rounds in 25 minutes. To spice it up a little I make the second to last round double points and the last triple.