This is so quick and simple and it works great. At home, in middle school, we have been doing it DAILY with the help of an old Instructional Fair workbook series Thematic oral language for daily use: Math, science, social studies, language arts, creative arts. There is a weekly topic (in our book it is owls, snakes, tigers, polar bears, etc.) and there is a sentence or two for each day. The sentences cover the topic from all different angles: language arts, science, social studies, math, and creative arts. For example, this is Week 35 for the sixth grade volume:
Week 35 - Seals, Sea Lions, and Walruses
Day One. Language Arts.
a. dad ive been studying seals and sea lions but why cant i tell the difference between the too of them
b. yes they do look alike but sea lions has longer flippers and are able to rotate them hind flippers dad answered
Day Two. Science.
a. me knowed everything on the science test mr english accept what a "pinniped" are
b. mr english replied sum animals has flippers which look like fins so theyre called pinnipeds or fin-footed
Day Three. Social Studies.
chuck lisa and barb seen some well-trained seals at the ringing brothers circus chuck telled us that scientists they think that seals can be learned to do tricks fairly easy cuz theyre as smart as cats and monkeys
Day Four. Math.
mail walruses can bee 12 foot long and way up to 3000 pounds even female walruses they can way over 1500 lbs said the guide at the shedd aquarium
Day Five. Creative Arts.
at the metropolitan museum of art in new york city ms smythe my art teacher seen a carving maked out of walrus tusk she feeled sad that hunters useta kill them animals just for their tusks
The teacher is given an answer key with weekly lists of the corrected sentences and the skills covered in each day's work. This Instructional Fair series of workbooks [authors, Sharon Altena and Jan Leik ; illustrator, Pat Biggs] from 1993 includes a volume for each grade 1 through 6.
v. 1. Grade 1 -- IF8401
v. 2. Grade 2 -- IF8402
v. 3. Grade 3 -- IF8403
v. 4. Grade 4 -- IF8404
v. 5. Grade 5 -- IF8405
v. 6. Grade 6. -- IF8406
Of course you could try to track down used copies, which would be easy and convenient, or you could simply create your own sentences! This is what Becca's teacher is doing, although she says it takes her a lot of effort to "write it wrong" when she's creating them.
Waldorf-wise, I would suggest this type of work for fourth grade and up.
Waldorf books for handwriting? The best is Teaching Children Handwriting by Audrey McAllen (which also includes how to teach the Capital Letters using the fairy tales). I also love the Form Drawing for Better Handwriting series (Volume 1 includes the entire series of second grade running forms in FD). And, lastly, I have Soul Development Through Handwriting: The Waldorf Approach to the Vimala Alphabet by Jennifer Crebbin.