Probably not, but there are a number of factors to consider, even if you moved out and graduated high school. Generally, you’ve got to live with someone for more than half a year to be their dependent.
Please see the TurboTax Help article Who can I claim as my dependent? for guidance in seeing if someone else can claim you.
Q. Am I considered a dependent if I moved out June 1st, but graduated high school in May?
A. No, unless you had less than $4300 of reportable income, for the year.
There are two types of dependents, "Qualifying Children"(QC) and standard ("Qualifying Relative" in IRS parlance even though they don't have to actually be related). There is no income limit for a QC but there is an age limit, student status, a relationship test and residence test. Only a QC qualifies a taxpayer for the Earned Income Credit and the Child Tax Credit. They are interrelated but the rules are different for each.
The support test is different for each type. The support test, for a QC, is only that the child didn't provide more than half his own support. The support test for a Qualifying Relative is that the taxpayer provided more than half the relative's support.
You cannot be a QC because you did not live with your parent for more than half the year (the residence test). It you had more than $4300 of income, you also cannot be a Qualifying relative. If you had less than $4300 income, we would then have to look at the other tests, mainly support.
See full dependent rules at: https://turbotax.intuit.com/tax-tools/tax-tips/Family/Rules-for-Claiming-a-Dependent-on-Your-Tax-Ret...