When trying to find information in the stream for Google Classroom you can use the keyboard shortcut of Control F to find a keyword. (Command F on a Mac.) You may need to scroll, scroll, scroll in the stream to reveal more assignments and announcements before using Control F. Google Classroom does not show all assignments and announcements if you have a lot of them in the stream. Scrolling reveals older posts.
My best Google Classroom tip is to number the assignments. This makes it a lot easier for students to locate the right assignment in the stream and also organizes the folders in your Google Drive Classroom folder. When numbering I suggest you use the pound symbol and use 3 digit numbers. ie: #001, #002, etc.. This makes it easier when trying to find assignments in the Google Classroom stream. Use Control F and type in, for example, #010 to find assignment 10. Since the numbering (including the hashtag) is unique, you can jump straight to that assignment quickly.