Will social security checks stop if you drop out of high school?

Yes this could be possible depending on the type of social security benefits that this question is about and the reason that they would be stopped by the SSA at the age of 18.

Go to the SSA gov web site and use the search box or find some contact information for your local SSA office to get the information that you want.

Your benefits will end with the payment for the month before the month in which you attain age 18. You attain age 18 on the day before your 18th birthday.

You can click on the below related link.