HTML Validating

Hello,

I teach a Web Design class to high schoolers.  I teach the students how to
validate their HTML and CSS through the W3 website.  However, this year we
have started having issues with your servers flagging our school district
IP as using the website excessively.  We have now been blocked from
validating since last week.  Why is this?  I have 18 students that are
trying to validate multiple pages of their websites and can not do so.  How
do we fix this?

Thank you,

*Mr. Damian Tate, MA*
Information Technology TEC
Boulder CTEC - BVSD
720.561.5239