How do school boilers work?
Unless it is a really old school I think most schools have gotten rid of boilers, at least here in CA. I know my school heating system was connected to a satellite that sent the message to turn on/ turn off, hot or cold to the computer in my school. My bet is that many schools are on this type of system now.
Are all water tube boilers suspended from overhead or set on columns to take care of expansion and contraction?
No. Most, like Stirling, B&W and Heine boilers are suspended from steel work with cleats or U-bolts, however some designs are not suspended. A small vertical water tube boiler could have been mounted on a base with the expansion from heating moving upwards. A Clayton steam generator is a coiled boiler mounted on a base. Robert's or Almy marine boilers are mounted on bases. Automotive water tube boilers were mounted on automotive frames.
There are various companies whom make electric boilers. Precision Boilers, Electric Heating Company, and Thermaflow Heating are to name just a few of the companies in which one may find a company that makes electric boilers. It is possible for one to contact the local electric company to inquire if they are a qualified agency that makes electric boilers.
How many boilers were built into design of the Titanic to provide the steam necessary to maintain this speed?
There are several ways in which you can get a Minnesota Special class boilers license. You can attend a 10 week training course offered in various areas of the state and take your test at your local secretary of state office. You can also attend formal training at a college which will take you longer but provide you with hands on training and take the certification test through the school.