Some manga are exactly what they seem to be from the very start. This is one of those manga.
Sensei Lock On! Starts out a fun 4-Koma manga about a 33-year old fourth grade teacher who has a very chaste boyfriend-girlfriend relationship with her 20-year old former student. It tells the same half dozen jokes over and over again. The first time, the jokes are fun and cute.
The fifth time, the jokes are starting to wear a little thin.
By Chapter 30... well, the jokes have worn out their welcome.
Now, that wouldn't matter much if their was character development or significant relationship building.
Rest assured: there is not.
I don't want to bash this manga too much. The art is great. The characters are a lot of fun, and I was rooting for them as a couple. And the jokes do start out funny, the first few times they are told.
I just wish the manga had either progressed a bit, or expanded it's comedic repertoire.
A generous, completely inoffensive 7/10.