https://www.cdc.gov/ncird/whats-new/measles-outbreak-risk-in-us.html
We are up to 128 measles cases so far this year in 19 states. The CDC expects around 300 cases by the end of the year. This would be one of the higher outbreaks in the last couple of decades.
Here's a good look at how infectious measles can be in a school of 100 students with 1 child infected with measles.
Nationally MMR vaccination among kindergartners is only 93%. In 12 states it is below 90%.