Cross curricular activities are great. But sometimes it's tough to marry two subject areas evenly. While using songs to teach addition, grammar, and other concepts is helpful for students, it may not truly be teaching or reinforcing musical concepts. Incorporating rhythm and poetry into a lesson can give both subjects equal attention.
I like to use haiku poems. They are fun, fairly easy to write, and come with a rich history. Students may even be learning about them in their reading class! A haiku is a traditional Japanese poem written in a 5-7-5 syllable pattern. When translating this into music, I use one syllable=quarter note and two syllables=eighth notes.
Pick a topic that you want your students to write about. Depending on the grade level and student ability you may choose to provide them with a word list or you may want to brainstorm words with students and categorize them into 1 or 2 syllable words. To help students determine how many syllables a word has, I have them place their hand under their chin and count the number of times their chin taps their hand while they say the word. If a word has more than 2 syllables, you may consider discarding it or fitting it across 2 rhythms (e.g. butterfly as 2 eighths and a quarter).
Guide students through the haiku 5-7-5 pattern and give them time to work on their own. After writing their poem, students can practice saying the rhythms and/or saying the words rhythmically.
Interested in incorporating rhythm haikus into your classroom but short on time? Check out my pre-made ones! They come with rhythm sheets, word suggestions, and slides briefly explaining haikus and how to write them.