Ninja Academy

 is the Specialty Building for the Ninja Monkey. It costs 750 to purchase its first upgrade and it also increases the cost of Sniper Monkeys by 5%. This Specialty Building was added in an update to Bloons TD 5 on 21st June, 2012.

Upgrades

 * Initial cost is 750
 * Second upgrade costs 750
 * Third upgrade costs 1750 (in the Mobile version it costs 750 and it makes shurikens last longer instead of having the Shadow Double Ability)
 * (Bloons TD5 Mobile only) Fourth upgrade costs 1750, adds Shadow Double Ability.

Tips
This building is generally unviable outside of early rounds due to the fact that regardless of the Ninja's upgrades, the Level IV ability always summons an extremely weak 0/0 Ninja (although in BTD5 Flash, it is always a copy of the respective Ninja, except Sabotage Supply Lines which just duplicates a Flash Bomb).

Trivia

 * This is currently the only Specialty Building which adds a Special Ability to the tower, not counting the iOS Bombing Range & Super Monkey Lair.
 * It is possible to have a Ninja Monkey with two different abilities at the same time, as long as this building's third upgrade is purchased and activated along with a Sabotage Supply Lines Ninja Monkey.
 * If you sell the Ninja Monkey while the special ability is still in use, the shadow will stay until the ability is finished.
 * If you have a Sabotage Supply Lines Ninja Monkey and you use the Shadow Double ability on it, you will not get another Sabotage Supply Lines ability.
 * It is possible to click on the shadow monkey and it will show you a pop count. However, it will reset when the ability ends.
 * The Ninja's Shadow Double Ability is possibly a reference to the Shadow Clone Technique in the Naruto manga/anime.
 * Increasing the cost of Sniper Monkeys can actually be a disadvantage because in the higher rounds people plan for a lot of Cripple MOABs. However, some people like to get Sabotage Supply Lines to slow down blimps and this lowers the cost of Ninja Monkeys (if you have tier I) so it's both good and bad.
 * As well as this, Supply Drop Snipers may be worth more than other money-generating towers in the later rounds, which may hinder the player's ability to buy them.
 * On Mobile, the shadow double ability always produces a 0-0 ninja regardless of the ninja's upgrades