I don't use chromebooks, but our school does use laptops for our students. Start the computers up ahead of time . Assign a computer team to turn them on 10 minutes before you will use them. Save Spelling City site on the desktop as a shortcut and students will launch from there. Log on for that site is quick and they should be going directly to assignments. Display a "How to Log on" poster and practice logging onto the site. My first grade students can do this fairly quickly and independently. Always have a book under the computer in case of computer, server, internet or website problems. Students will wait patiently if they have something to keep them busy while waiting for help.