To stop MR WACKER expelling ERIC after 10000 lines:

POKE 7528,2 ($1D68,$02)

To prevent teachers from giving lines to ERIC or anyone else:

POKE 7607,96 ($1DB7,$60)

However, that won't prevent MR WACKER from giving ERIC 2000 lines during the 'special' playtimes (if EINSTEIN tells WACKER what ERIC's up to, or WACKER finds the pea-shooter on the fire escape). For that you need:

POKE 10127,0 ($278F,$00)

One harmless side effect of this POKE is that the lines total will be printed as '00' instead of '0' when WACKER delivers his 'TAKE 2000 LINES...' speech.

To make sure that EINSTEIN never tells tales:

Alternatively, to make the teacher always give lines to EINSTEIN for telling tales:

POKE 9561,0 ($2559,$00)

Hitting all 15 shields before obtaining the safe combination, and then hitting all 15 shields again after opening the safe can be hard work for a busy skoolboy. To reduce ERIC's task to hitting just one shield (any shield):

POKE 11313,1 ($2C31,$01)

Note that in order to go up a year, ERIC will have to hit the same shield as he hit before opening the safe.

Having to knock down the teachers (or, in CREAK's case, discover his year of birth and then write it on the blackboard in the classroom he'll be teaching in next) in order to obtain the safe combination letters, and then try up to six permutations of those letters before hitting the right one, can be a tiresome task. How much easier it would be if BOY WONDER and the teachers took it upon themselves to reveal the safe combination (stored at $90) every time they wrote on a blackboard:

The teachers and BOY WONDER will actually write the safe combination followed by CREAK's year of birth on the board, but the birth year can be ignored.

Compared to the ZX Spectrum version, ERIC seems to amble along with no sense of urgency at all, which can be rather frustrating (especially when being chased back to class by a teacher). To make ERIC pick up the pace a little:

To extend the range of the catapult from 13 to N:

POKE 11137,N ($2B81,N)

However, this doesn't extend the 'hit zone' of the pellet (the portion of its flight where it can hit something). To change the hit zone from the last 7 stages of its flight to the last M stages (M=N-6 is a good choice):

POKE 4106,M+1 ($100A,M+1)

To enable ERIC to walk through specific walls: