UIL vs NCAA differences

[Atlanta Blue]

Not to muck up another post, and just for my own knowledge, what are the differences between NCAA and UIL rules?  And isn't there another "governing body" in Texas as well?  Do they use the same rules as the UIL?  What about Massachusetts?

I know some differences: 12 minute qtrs, kickoff from the 40.  Are goal posts HS width (23'4") or NCAA width (18'6")?  What about the hashes?  Knee pads covering the knees?  Other "safety" issues?

Just wondering.  I know people say Texas and Massachusetts use "NCAA rules", but obviously, it's "modified NCAA Rules".  How modified?

[Getting Fat]

http://www.safootballchapter.us/2010TxHSExceptions.pdf

Primarily timing differences. 

[NVFOA_Ump]

Attached is the "complete" list of what Massachusetts uses.  "Major differences" are:

1.  Always a 25 sec play clock
2.  INC passes / ball OB, clock on the snap
3.  10, 11, or 12 minute periods (varies by league)
4.  5 timeouts (3-90 secs, 2-30 secs)
5.  KO's at the 40 yard line

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[Welpe]

Blue, there is also TAPPS here in Texas. Texas Association of Private and Parochial Schools.  I believe they also play by the same UIL exceptions.