It is possible to add students when your spirit is within 25% of your enrollment (neutral face displayed on the spirit indicator), but once you pass that threshold, your spirit indicator will return to a frown face and you can no longer do things with your residential buildings (including move them to storage).

Please note that the Admissions Building, while found in the Residential Build tab, is not in the game to increase enrollment. It adds Alumni (+5% of your enrollment) and Coins (+10% of your enrollment) without decreasing enrollment. Alumni currently have no function in the game.

The Chart below shows the rate of return per grid square (not per building) based on a set check time.

Residence___Build___Student__Grid__Rec harge_Income_per_grid_square
Name______Cost___Income___Size__Tim e_2.5m_15m_1.5h_3h_6h_12h_
Small Dorm__$3,500_2_1__0:02.5_ 2.00_2.00___2.00___2.00___2.00___2.00
BA Frat_____$5,000__5__2__0:10___0.63__2.50__2.50__2.50___2.50__2.50
Victorian Sorority__$6,000___4__2__0:08__0.63 __2.00__2.00__2.00_2.00_2.00
Gray Common House_$10,000__8__1_0:30__0.67_4.00__8.00__8.00__8.00_8.00
Tudor Frat___$12,000__15_2__0:40__ 0.47__2.81__7.50__7.50__7.50__7.50
Gabled Sorority_$15,000__12__2__0:32_0 .47_2.81__6.00_6.00__6.00__6.00
Tiny Apt._____$16,000__6_1__0:15__1.00__6.00__6.00___6.00___6.00__6.00
Small Apt.___$24,000__20_1_1:30_ 0.56___3.33__20.00__20.00__20.00__20.00
Large Dorm___$25,000__18__2__1:00__ 0.38__2.25_9.00__9.00_9.00__9.00
Large Apt.____$47,500__40__2__6:00_ 0.14_0.83___5.00__10.00__20.00__20.00
Brown Common__$60,000_30__2__4:00_ 0.16__0.94__5.63__11.25__15.00_15.00
Hotel_______$80,000__60__2__12: 00__0.10__0.63_3.75_7.50__15.00__30.00
High Rise Apt.__$125,000_80__2__24:00__0.07 _0.42__2.50_5.00__10.00__20.00
Red Common House_$150,000_75_2_18:00_0.09_0.52_3.13_6.25_12.50_25.00

Example 1 - If you're checking the game every 15m, you'll have 2 students per grid square ready. Small dorm takes 2 grid squares so that's as far as you need to read. If you were checking more frequently, the Small Dorm would have been ready every 2.5 minutes - and could have produced 12 students in 15m with constant monitoring.

Example 2 - If you're checking every 3h, Each Small Dorm will have only produced 2 students per grid in that time, but each Large Dorm will have produced 9 students per grid square. Since the Large Dorm take 2 squares, that adds up to 18 students per Large Dorm in that time frame. If you were checking more frequently, the Small Dorm would have been ready every 2.5 minutes - and could have produced 144 students, but the Large Dorm would still have only produced 18 students because of its 1h recharge time.