Yes, lark is a Scrabble word!
...and is worth 8 points in Scrabble, and 9 points in Words with Friends
lark
Verb
1. Play boisterously
Noun
1. North American songbirds having a yellow breast
2. A songbird that lives mainly on the ground in open country; has streaky brown plumage
3. Any of numerous predominantly Old World birds noted for their singing
4. Any carefree episode
What Scrabble words can I make with the letters in lark?
3 Letter Words
2 Letter Words