Hemingway App
I recommend Hemingway Editor for finding run on sentences or improving readability and clarity:
REWORDIFY
Rewordify is good for reading difficult texts. Use it to show up hard words. You can also use it to improve your readability and clarity.
GRAMMARLY
The free version of Grammarly will check Spelling, Grammar and Punctuation. If you have trouble finding where the missing capitals are then this one is for you. You will need to sign up though. So you can use it at school, I recommend signing in with your Microsoft login (Learnlink).
Language tool
This one is free for 20,000 characters at a time and will pick up common homophones (your, you’re) and some capitals.
Scribens
This one is free, and good at picking up run on sentences; but not easy to use.